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Chapter 01: System of linear Equation and Matrix V2 — Transcript

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  1. 0:00foreign
  2. 0:00[Music]
  3. 0:09we talk about the system of equation
  4. 0:11algebraic procedure
  5. 0:14outcome
  6. 0:16in our system equation you can use
  7. 0:19Elementary operation to find solution to
  8. 0:23a linear equation
  9. 0:27the next point you can find row Echelon
  10. 0:29form and reduce row Echelon form from a
  11. 0:32matrix
  12. 0:35determine whatever system of linear
  13. 0:37equation has no solution unique solution
  14. 0:40and an Infinity number of solutions from
  15. 0:43each row each landform
  16. 0:46so a system of equation using gaussian
  17. 0:49elimination or both your tongue
  18. 0:51elimination
  19. 0:53model or physical system with linear
  20. 0:56equation and tensor
  21. 0:58so this is the way that you can solve
  22. 1:01about the system of linear equation you
  23. 1:04have five way
  24. 1:05to Seoul and when you study metric you
  25. 1:09can solve the system or linear equation
  26. 1:10by inverse metric also
  27. 1:13in your class now it is not only by
  28. 1:16substitute
  29. 1:17by addition and by graph you can solve
  30. 1:24sum of system equation by Elementary row
  31. 1:27operation by row Echelon form by
  32. 1:30gaussian by goshok long or by
  33. 1:37you have more about this one so about
  34. 1:41the system of linear equation
  35. 1:44and
  36. 1:46we have take an in-depth look at
  37. 1:50graphical representation of system of
  38. 1:53equation
  39. 1:54as well how to find possible solution
  40. 1:57graphically
  41. 1:58our attention now is turned to work with
  42. 2:01system algebraically
  43. 2:05definition of system of linear equation
  44. 2:08a system of linear equation is a list of
  45. 2:11equation so when you write
  46. 2:16a 1 1 x 1 plus a 1 2 x 2 equal to B1 so
  47. 2:22this is only equation
  48. 2:26we call this this equation
  49. 2:29when you write in list
  50. 2:31this is one equation one equation two
  51. 2:34and equation m
  52. 2:37because from 1 to M this is m
  53. 2:40equation
  54. 2:43M equation you write in a list we can we
  55. 2:47can call this we cannot call this system
  56. 2:49equation we call this is the system of
  57. 2:52linear equation you can write in curly
  58. 2:55blanket or you can write in the list of
  59. 2:57uh equation we call this is the system
  60. 3:00of unique way equation
  61. 3:04uh where a i g AIG so I is
  62. 3:11uh like row
  63. 3:14and J this is like column
  64. 3:19killer muscle
  65. 3:20so this is
  66. 3:24AIG it means that the position of
  67. 3:28uh a that stand in row I and column J
  68. 3:34and BJ are real number so a
  69. 3:39and B is real number is belonged to
  70. 3:43real number
  71. 3:45the ball of system of M equation in the
  72. 3:48in the N word variable
  73. 3:52X1 X2 and T2 x n this is n variable
  74. 3:57so we can write in this form
  75. 4:00from this
  76. 4:01system linear equation we can write to
  77. 4:04this one
  78. 4:06is Sigma J from 1 to n a
  79. 4:10a i j x j equal to b i
  80. 4:13is from one two three four until m
  81. 4:20and that is related to our system
  82. 4:24equation
  83. 4:25this is system equation none
  84. 4:32homogeneous
  85. 4:35uh homogeneous
  86. 4:39this is the system of linear equation
  87. 4:43non-omogenous because the right hand
  88. 4:45side it is not equal to zero
  89. 4:48if it is not equal to 0
  90. 4:52this is non-omogeneous system of linear
  91. 4:55Equity equation
  92. 4:58and homogeneous system of linear
  93. 5:01equation this form
  94. 5:03it means that the right hand side
  95. 5:06this is equal to zero it means that b i
  96. 5:11if b i
  97. 5:13I from 1 to m
  98. 5:16equal to 0
  99. 5:18this equation we can call the system
  100. 5:20equation we can call
  101. 5:22the system of homogenous system of
  102. 5:25equity equation
  103. 5:29uh aij
  104. 5:32Alia scalar scalar it means that this is
  105. 5:37constant number
  106. 5:39and X I already variable
  107. 5:44so the
  108. 5:46consistent and inconsistent
  109. 5:51so please remember that point what is
  110. 5:55consistent
  111. 5:56and what is inconsistent
  112. 5:59system equation
  113. 6:04system equation
  114. 6:07now a system of linear equation is
  115. 6:11called consistent if there exists at
  116. 6:14least one solution
  117. 6:17so the system that have only one through
  118. 6:20at least one solution at least one
  119. 6:23solution it means that
  120. 6:25have one solution two solution three
  121. 6:29solution or more than three or Infinity
  122. 6:32solution
  123. 6:33at least you know at least at least it
  124. 6:36may not start from one
  125. 6:38can be one two three and four until two
  126. 6:41Infinity
  127. 6:43so if the system or linear equation
  128. 6:46have at least one solution we can call
  129. 6:49the system is consistent
  130. 6:51we can call consistent
  131. 6:55this is consistent
  132. 6:57if the system have no solution
  133. 7:01if the system have no solution we can
  134. 7:05call this system of linear equation this
  135. 7:08is inconsistent
  136. 7:10consistent it means that have at least
  137. 7:13one solution
  138. 7:15inconsistent it means that has no slow
  139. 7:17no solution so this is the opposite
  140. 7:21between consistent and inconsistent
  141. 7:24consistent it means that you have
  142. 7:27at least one solution and inconsistent
  143. 7:30you have
  144. 7:33no slow no solution in here
  145. 7:38uh
  146. 7:39Elementary row operation
  147. 7:42so now we will talk about the element
  148. 7:44three row operation
  149. 7:48Elementary over row operation is begin
  150. 7:50this section with an example
  151. 7:54example verify
  152. 7:57an order pair of a solution
  153. 8:01algebraic verify that X and Y minus 1
  154. 8:05and 5 is a solution of
  155. 8:08a system of equation is here which I
  156. 8:12explained you from a bio point we have
  157. 8:16equation One X Plus y equal 3 and Y
  158. 8:19minus x equal to Phi the intersection
  159. 8:22between Line 1 and line two at the point
  160. 8:25x 0 equal to
  161. 8:27negative 1 and y 0 is equal to 4.
  162. 8:32424
  163. 8:33so this solution is like
  164. 8:36example you use about
  165. 8:39equation one
  166. 8:41equation one you use x equal to -1 and y
  167. 8:46equal to four this is equal to 3.
  168. 8:49and equation two is also you use uh our
  169. 8:53equation one is
  170. 8:55X Plus y equal to 3 and Y minus a equal
  171. 9:01to 5.
  172. 9:03equal to Phi
  173. 9:05so now you got this point in uh when you
  174. 9:09start to shoot when you substitute
  175. 9:12negative one and four
  176. 9:15negative one and four into equation 1
  177. 9:18and into equation two you got
  178. 9:21equation one is X plus three plus y
  179. 9:25equal to 3 is true
  180. 9:28true because
  181. 9:30minus one plus four
  182. 9:32equal to 3 and
  183. 9:35y minus x equal to 5 also true
  184. 9:40because uh 4
  185. 9:43uh minus and minus 1 equal to 5. so
  186. 9:48a equal to negative one and five and y
  187. 9:53equal to 4 this is a solution of our
  188. 9:56system in the aqua equation
  189. 10:01so now we got this is
  190. 10:04system or linear equation have only one
  191. 10:06solution negative one and four
  192. 10:11and Elementary row operation
  193. 10:14Elementary Pro operation Elementary
  194. 10:17operation are those operations
  195. 10:19consisting
  196. 10:21of the following
  197. 10:24the first you can interchange the other
  198. 10:28in each patient at least
  199. 10:31example in here
  200. 10:33you have uh X Plus y equal three
  201. 10:39and Y minus X
  202. 10:42equal Phi so you can write y minus X
  203. 10:46equal Phi and
  204. 10:50x minus y equal to 3. so this is in the
  205. 10:54chain Row in our list you can change
  206. 10:59and point two multiply an equation by
  207. 11:02non-zero none's row number
  208. 11:05so in here this is also you can
  209. 11:09uh multiply
  210. 11:12example I write uh
  211. 11:155y minus pi x
  212. 11:19equal to 25 and
  213. 11:23uh
  214. 11:2510 x
  215. 11:27plus 10 y equal to 0 30. so I can
  216. 11:31multiply an equation with non-zero num
  217. 11:35non-zero number
  218. 11:38and replace an equation with its cell at
  219. 11:422 multiply another
  220. 11:44uh
  221. 11:47equation it means that example
  222. 11:50I have X
  223. 11:52plus y equal to 3 and X
  224. 11:55minus y equal to Phi
  225. 11:58so in this here I done one I don't want
  226. 12:01to uh
  227. 12:05I don't want to
  228. 12:07add equation one and equation two so I
  229. 12:10write this one is
  230. 12:11multiply with negative one I got X Plus
  231. 12:14y
  232. 12:16equal to 3 and
  233. 12:18Negative X
  234. 12:20plus y equal to minus 5. so I can
  235. 12:23addition this is 2X
  236. 12:26equal to minus minus four so X
  237. 12:302 y equal to
  238. 12:33uh
  239. 12:35the place that you you think it means
  240. 12:38that minus one this is plus and minus so
  241. 12:41this is only uh minus two you got minus
  242. 12:46two so you got y this is
  243. 12:49equal to the point that you think
  244. 12:53the point the other uh solution that we
  245. 12:56want to make we want to find in this
  246. 12:58area
  247. 13:00and
  248. 13:02it's important to not
  249. 13:04that none of this operation will change
  250. 13:07the set solution of the system equation
  251. 13:11so when you
  252. 13:13exchange about the role
  253. 13:17to
  254. 13:18Row 1 and Row one to Row 2 and Row 2 to
  255. 13:21row three or Row one row two you get
  256. 13:24from
  257. 13:25row two
  258. 13:28plus k ro1 and something so our solution
  259. 13:32it is not the same solution it is not
  260. 13:35uh another solution in here please
  261. 13:39remember that not change about the
  262. 13:41solution when you interchange order in
  263. 13:44which equation list multiply in the
  264. 13:47equation by none's row or replace
  265. 13:49equation with its cell add to a multiply
  266. 13:52of a multiple of another equation so it
  267. 13:56is not changed
  268. 13:57it the same solution
  269. 14:02example effect and Elementary operation
  270. 14:06so that the system
  271. 14:09X
  272. 14:10Plus
  273. 14:11y equal to 7 and 2x minus y equal to a
  274. 14:18has same solution as system X Plus y
  275. 14:22equal to so n and negative
  276. 14:273y equal to 3x
  277. 14:30so
  278. 14:31they want you to show us about this
  279. 14:34system equation and this is some system
  280. 14:37equation have the same slow solution
  281. 14:42so notice that the second system has
  282. 14:45been obtained by taking the second
  283. 14:48equation of the first system
  284. 14:51-3 minus 2 time
  285. 14:54first equation as this one
  286. 14:58so
  287. 15:00it means that the second question
  288. 15:03get from
  289. 15:05get from
  290. 15:07the first system adding
  291. 15:10the first system adding two
  292. 15:13time on the first equation
  293. 15:16to time on the cross equation so this is
  294. 15:19first equation
  295. 15:21and per system so I add two time to time
  296. 15:25it means that
  297. 15:26this is multiplied by minus two
  298. 15:30so I got minus 2X
  299. 15:33uh minus 2y equal to minus 14. and this
  300. 15:39is 2x minus 2y
  301. 15:42equal to uh
  302. 15:45a
  303. 15:46equal to a
  304. 15:49so now we can check
  305. 15:52we can check this one it's all
  306. 15:55and this is for
  307. 15:58y equal to this one is like
  308. 16:03uh
  309. 16:04uh six
  310. 16:07minus minus six yeah
  311. 16:10so
  312. 16:12this one maybe
  313. 16:13four yeah is minus minus six
  314. 16:18so this equation
  315. 16:20this equation is
  316. 16:22get from the
  317. 16:24system one
  318. 16:27take the first equation multiply by
  319. 16:30negative 2 18 with the equation two so
  320. 16:34you got this result
  321. 16:37and for the next
  322. 16:44for the next verify this is
  323. 16:49and within the current equation is a
  324. 16:52second system now
  325. 16:54uh
  326. 17:002x negative y
  327. 17:06we got this one is four it's not uh
  328. 17:09three
  329. 17:11this is four
  330. 17:15negative 4.
  331. 17:19and now we check
  332. 17:23we check it means that X Plus y equal to
  333. 17:265 plus 2 is
  334. 17:287 and 2x minus y
  335. 17:33substitute x equal Phi and y equal to
  336. 17:36this is equal to eight so this is
  337. 17:40uh
  338. 17:41there is a I mean that it is certified
  339. 17:45left hand side and right hand side
  340. 17:49hang Phi and 2 is also a solution of the
  341. 17:53first equation
  342. 17:54of first equation
  343. 17:57so the next point we will talk about the
  344. 17:59elementary row operation and solution
  345. 18:03suppose you have a system of two linear
  346. 18:05equations
  347. 18:07we can let E1 equal to B1 E2 equal to B2
  348. 18:13and E2 equal to B2 E1 equal to B B1 so
  349. 18:18this is we can change each other
  350. 18:21and the next the point two
  351. 18:25we multiply equation two
  352. 18:29Vision Two by K
  353. 18:32by K
  354. 18:34but K it is not equal to 0 besides 0.
  355. 18:39K is provide K opposite of zero
  356. 18:43so three you got
  357. 18:47you can addition between equation 1 and
  358. 18:50equation two
  359. 18:51it means that
  360. 18:54uh
  361. 18:56you got about E2 plus ke1 equal to B2 uh
  362. 19:02plus KB case B1
  363. 19:07k
  364. 19:08including k equal to zero
  365. 19:12for an EK
  366. 19:14scalar okay including k equal to 0 also
  367. 19:17in here
  368. 19:19so now before we proceed with a proof of
  369. 19:25serum 1.8
  370. 19:28let us consider this serum in contact of
  371. 19:33our example
  372. 19:35E1 we let E1 is equal to
  373. 19:39X
  374. 19:41plus y B1 equal to 7
  375. 19:44E2 2x minus y
  376. 19:48and B2 is equal to X
  377. 19:51equal to a
  378. 19:53so now
  379. 19:55now we recall Elementary row operation
  380. 19:58we use to modify system in solution to
  381. 20:01example
  382. 20:03first we add
  383. 20:06we add
  384. 20:07negative two times
  385. 20:10the first equation to the second
  386. 20:13equation in term of
  387. 20:16uh serum 1.8 this section is given by
  388. 20:21it means that
  389. 20:22we add
  390. 20:24minus two times our first equation minus
  391. 20:28two times our first equation
  392. 20:30to time of first equation
  393. 20:35uh to the current equation so second
  394. 20:37equation you got the current equation
  395. 20:41get from
  396. 20:43second equation Plus
  397. 20:45negative time of
  398. 20:48equation equation one
  399. 20:51so this is meaning
  400. 20:53so now we got
  401. 20:57this
  402. 20:59equation E1 equal B1 and E2 minus two uh
  403. 21:04E1 equal to B2 minus uh
  404. 21:08B1
  405. 21:10so now we got
  406. 21:13we got E1 equal B1 and E2 equal to b e
  407. 21:17B2
  408. 21:20this is our result that we can check all
  409. 21:24together about this point
  410. 21:26and finally we can
  411. 21:30find one by one like B1 equal B1 and E2
  412. 21:34equal to B B2 or E2 plus ke1 equal B1
  413. 21:39plus K B1 so we obtain E2 equal B2 and
  414. 21:43E1 equal to B B1 in our receptify
  415. 21:50uh sold a system linear equation with
  416. 21:53Elementary operation
  417. 21:56so this is our system of
  418. 22:01uh
  419. 22:02linear equation so they want us to solve
  420. 22:05the system of linear equation with
  421. 22:07Elementary row operation find the
  422. 22:10solution to this the system
  423. 22:13so we can relate this system of
  424. 22:16serum 1 8 above in case we have
  425. 22:21we let E1 is equal to X Plus 3y plus six
  426. 22:25disease and B1 is equal to 25 E2 is also
  427. 22:29and E3 is also
  428. 22:32so now this is our equation
  429. 22:35this is our equation and this is our
  430. 22:39left letting
  431. 22:41but in the definition we can first
  432. 22:44replace the current equation by two time
  433. 22:47the first equation add to the second
  434. 22:50this year
  435. 22:52so it means that
  436. 22:55we can
  437. 22:59use we can use the second equation
  438. 23:02by replace the current equation by two
  439. 23:06time of
  440. 23:08first equation A2 second it means that
  441. 23:12you take this one divided by multiply by
  442. 23:16negative 2 and plus 2 equation two and
  443. 23:21plus through this equation
  444. 23:23so this one divided by 2 multiplied by
  445. 23:25negative 2 is 2X
  446. 23:28minus
  447. 23:306y
  448. 23:32minus
  449. 23:34well equal to minus 50.
  450. 23:37and 2x
  451. 23:40plus so when y
  452. 23:43plus 14
  453. 23:47Z equal to
  454. 23:4958 so you can add in is no X
  455. 23:53so this is uh
  456. 23:55so when y minus 6y is only y
  457. 23:5914 minus 12 is 2.
  458. 24:02to Z equal to a so we got this one
  459. 24:07now
  460. 24:08and also in
  461. 24:12equation 3 is only
  462. 24:142y
  463. 24:15plus pi Z equal to 9 19 is the the same
  464. 24:21here
  465. 24:22so now we can check for
  466. 24:26our replacement to equation two
  467. 24:29time second add to sir
  468. 24:33so now you got this is
  469. 24:37second
  470. 24:40answer so if you want to
  471. 24:44omit it y you can write 2y minus 2y
  472. 24:48minus 4 Z equal to minus 16.
  473. 24:53and this is 2y
  474. 24:55plus pi Z
  475. 24:57equal to 9 19 so it's no Y in here this
  476. 25:02is z equal to 3. so now we can check all
  477. 25:06together
  478. 25:07so Z is equal to 3 in here so this is we
  479. 25:12got about this is our equation system
  480. 25:14equation when you know the value of Z
  481. 25:17you can find about the value of y by
  482. 25:20substitute Z equal to 3.
  483. 25:23when you know the value of y in here I
  484. 25:26write y0 you can find the value of a
  485. 25:29fake because you know y you know Z so
  486. 25:32you can substitute the value of Z and
  487. 25:36you can substitute the value of y you
  488. 25:38got the value of object in here
  489. 25:42so this way they can call disease
  490. 25:45Elementary or pre operation or
  491. 25:48Elementary row Opera a row operation
  492. 25:51please remember about this point
  493. 25:54so you got set Z equal to 3 y equal to 2
  494. 25:59and x equal to 1 by our circuit
  495. 26:01substitute so
  496. 26:04solution of this equation is X Y and Z
  497. 26:07equal to 1 2 and 3.
  498. 26:12the process is callback subtit
  499. 26:14substitute alternative in one point when
  500. 26:18you could have
  501. 26:19continue as follow at
  502. 26:22negative two times the equation to
  503. 26:25second or then at six
  504. 26:28negative 6 times to turn to the first
  505. 26:32this is up to you so we also get the
  506. 26:35same solution
  507. 26:37x equal to 1 z y equal to 2 and Z equal
  508. 26:43to 3 also
  509. 26:44so all the point which I taught you
  510. 26:48today it means that I only talk about
  511. 26:50the system equation and how to solve the
  512. 26:53system of equation by changing into
  513. 26:56chain about the role or in the chain
  514. 26:58about the equation in our list or can
  515. 27:02multiplication
  516. 27:03none's row number in other equation and
  517. 27:08you can solve the system of linear
  518. 27:10equation by Elementary row operation
  519. 27:12so now we have continued to study about
  520. 27:16the uh how to solve the system or linear
  521. 27:20equation by ghost chin elimination
  522. 27:25in here
  523. 27:28now we can check for the next point for
  524. 27:31the next point
  525. 27:34now we go to gushing elimination
  526. 27:39what is gaussian elimination
  527. 27:41example when you have
  528. 27:44I will explain you in here
  529. 27:47when you have a x a 1 x 1 plus A2 A1 2 x
  530. 27:552
  531. 27:56and plus a13 X3
  532. 28:00equal to B1
  533. 28:03a21 X1
  534. 28:05plus a 2 2
  535. 28:07x 2 plus a 2 3
  536. 28:10x 3 equal to B2
  537. 28:14a31 X1 Plus
  538. 28:17a 3 2 x 2 plus a33
  539. 28:23take three equal to B B3
  540. 28:26so this is the form of
  541. 28:30uh
  542. 28:32system linear equation B if we want to
  543. 28:36find about the system of linear equation
  544. 28:38by gaussian elimination you we convert
  545. 28:41from this equation to H1 Matrix
  546. 28:54to H1 metric here
  547. 29:00to each one
  548. 29:03Matrix
  549. 29:04like H1 Matrix you just only write about
  550. 29:08the
  551. 29:09the constant in our system
  552. 29:11in our system
  553. 29:13so you can write a11
  554. 29:16a12
  555. 29:18a13
  556. 29:19and B1
  557. 29:22a21
  558. 29:24a tool
  559. 29:26a23 and B2
  560. 29:2981
  561. 29:3182 and a33
  562. 29:34is this B B3
  563. 29:37so when you got this H1 Matrix gaussian
  564. 29:40elimination is f the same
  565. 29:43a11
  566. 29:45a12
  567. 29:47a13
  568. 29:49B1 this one is zero zero and this is
  569. 29:53only I can call this is K
  570. 29:58and this is also K1
  571. 30:01uh
  572. 30:02is it p p and zero zero and also uh m
  573. 30:10equal to l
  574. 30:12Prime
  575. 30:14so this is
  576. 30:16the kind or the form of gushing eliminae
  577. 30:21which in a limitation or we can call
  578. 30:23this is upper triangular main metric or
  579. 30:27so so the next point you will know about
  580. 30:29this I will explain you this is only my
  581. 30:32draft or my shortest explanation how can
  582. 30:37you do a gaussian elimination with
  583. 30:39system of unique way equation
  584. 30:42now we can check this is only my
  585. 30:46explanation which I told you already
  586. 30:49when you want to so you should be
  587. 30:52changed from the system line equation to
  588. 30:55argument May a metric example this is we
  589. 30:58have about the system of unique way in
  590. 31:01the equation
  591. 31:02so this system can be right as a
  592. 31:04treatment Matrix as follow so this one
  593. 31:07yeah when we have the system of linear
  594. 31:10equation we can go to uh h1ma H1 Matrix
  595. 31:15H1 metric we can use only the
  596. 31:18coefficient of variable
  597. 31:20or you can say use only the constant of
  598. 31:24equation
  599. 31:25so this is the constant or coefficient
  600. 31:28of this one three six twenty two
  601. 31:34seven Fourteen and eighteen so this is 0
  602. 31:38x
  603. 31:39plus 2y so we have one
  604. 31:43we have three we have six this is 20 25
  605. 31:482
  606. 31:501 14 and
  607. 31:5358 and this is zero
  608. 31:56this is 2
  609. 31:58this is 5 and this is 8 9 19. so
  610. 32:04achievement Matrix you can take only the
  611. 32:06constant
  612. 32:08we can stand
  613. 32:11with our equation to write in
  614. 32:15this one in metric we call this is Row
  615. 32:18one row one this is row two and this is
  616. 32:22called row row three this is column one
  617. 32:27alarm 2 and this is Kalam column 3 also
  618. 32:32so when you want to find solution of
  619. 32:36equation by gaussian elimination you
  620. 32:38should be convert from
  621. 32:40system equation to the H1 Matrix Plus
  622. 32:45[Music]

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