Ex 1: Evaluate a Natural Logarithmic Expression Using the Properties of Logarithms — Transcript
Full transcript
- 0:00- WE WANT TO EVALUATE THE LOGARITHMS
- 0:02GIVEN NATURAL LOG X = 3, NATURAL LOG Y = 4,
- 0:06AND NATURAL LOG Z = 5.
- 0:09SO TO EVALUATE THESE,
- 0:10WE'LL EXPAND THESE LOGARITHMS AS MUCH AS POSSIBLE
- 0:13USING THE PROPERTIES OF LOGARITHMS
- 0:15AND THEN PERFORM SUBSTITUTION
- 0:17FOR NATURAL LOG X, NATURAL LOG Y, AND NATURAL LOG Z.
- 0:21SO LOOKING AT THE FIRST LOGARITHM,
- 0:23NOTICE HOW WE HAVE NATURAL LOG OF A QUOTIENT
- 0:26AND SINCE WE HAVE THE NATURAL LOG OF A QUOTIENT
- 0:28WE CAN EXPAND THIS TO THE DIFFERENCE OF TWO LOGARITHMS
- 0:32USING THE QUOTIENT PROPERTY GIVEN HERE.
- 0:35WHERE WE'LL HAVE THE LOG OF THE NUMERATOR
- 0:37MINUS THE LOG OF THE DENOMINATOR.
- 0:40SO THIS IS EQUAL TO NATURAL LOG X CUBED MINUS
- 0:46BECAUSE OF THE QUOTIENT NATURAL LOG Y SQUARED Z.
- 0:51NOW LOOKING AT THE SECOND LOG,
- 0:53NOTICE HOW WE HAVE NATURAL LOG OF A PRODUCT
- 0:56WHICH WE CAN EXPAND USING THE PRODUCT PROPERTY OF LOGARITHMS
- 0:59GIVEN HERE WHERE LOG X x Y = LOG X + LOG Y.
- 1:07WE HAVE TO BE CAREFUL HERE
- 1:08BECAUSE IF WE'RE SUBTRACTING THIS SECOND LOGARITHM
- 1:10WE'LL HAVE TO SUBTRACT THE EXPANSION
- 1:13OR THE SUM OF THE LOGARITHMS.
- 1:15SO THIS IS EQUAL TO NATURAL LOG X CUBED
- 1:20AND THEN MINUS THE SUM OF THE TWO LOGS
- 1:24WHICH WOULD BE NATURAL LOG Y SQUARED + NATURAL LOG Z.
- 1:33IF WE LEAVE OFF THESE BRACKETS
- 1:35NOTICE HOW WE'D ONLY BE SUBTRACTING
- 1:36THE FIRST LOGARITHM WHICH WOULD BE INCORRECT.
- 1:39AND NOW FOR THE NEXT STEP,
- 1:41WE'RE GOING TO APPLY THE POWER PROPERTY OF LOGARITHMS
- 1:43GIVEN HERE
- 1:44WHERE WE CAN TAKE THE EXPONENT HERE AND HERE
- 1:48AND MOVE IT TO THE FRONT.
- 1:52SO NOW WE WOULD HAVE 3 NATURAL LOG X - 2 NATURAL LOG Y
- 2:02AND + NATURAL LOG Z.
- 2:05NOTICE IN THIS FORM,
- 2:07WE CAN NOW SUBSTITUTE FOR NATURAL LOG X, NATURAL LOG Y,
- 2:10AND NATURAL LOG Z.
- 2:12IF WE WANTED TO WE COULD CLEAR THESE BRACKETS
- 2:13BY DISTRIBUTING -1,
- 2:16BUT LET'S GO AHEAD AND LEAVE IT IN THIS FORM.
- 2:18SO WE'D HAVE 3 x NATURAL LOG X WHICH IS EQUAL TO 3, MINUS
- 2:24AND THEN IN BRACKETS THE QUANTITY 2X NATURAL LOG Y
- 2:28WHERE NATURAL LOG Y IS 4 PLUS NATURAL LOG Z WHICH IS 5.
- 2:35SO THIS WOULD BE 9 - THIS WOULD BE 8 + 5 OR 13.
- 2:41AND 9 - 13 IS EQUAL TO -4.
- 2:49OKAY. LET'S TAKE A LOOK AT OUR SECOND EXAMPLE.
- 2:53THE FIRST THING WE SHOULD DO HERE
- 2:54IS WRITE THE SQUARE ROOT USING A RATIONAL EXPONENT.
- 2:58IF WE HAVE THE SQUARE ROOT OF "A,"
- 3:02BECAUSE IT'S A SQUARE ROOT THE INDEX WOULD BE 2,
- 3:04THE EXPONENT WOULD BE 1.
- 3:06THIS IS EQUAL TO "A" TO THE 1/2 POWER,
- 3:09WHICH MEANS YOU CAN WRITE THIS
- 3:11AS NATURAL LOG X SQUARED Y TO THE 3rd,
- 3:16Z TO THE 5th TO THE 1/2 POWER
- 3:21AND IN THIS FORM WE HAVE POWERS RAISED TO POWERS,
- 3:25SO IF WE HAVE "A" TO THE M RAISED TO THE POWER OF N
- 3:30THE RULE IS THAT WE MULTIPLY THE EXPONENTS.
- 3:33SO LET'S GO AHEAD AND DO THAT.
- 3:37THIS IS EQUAL TO NATURAL LOG, 2 x 1/2 WOULD BE 1
- 3:41SO JUST X TO THE 1st, Y TO THE 3 x 1/2 OR Y TO THE 3/2 POWER
- 3:49AND THEN Z TO THE 5 x 1/2 WOULD BE Z TO THE 5/2 POWER.
- 3:55AND NOW WE CAN EXPAND THIS.
- 3:57NOTICE HOW WE HAVE A PRODUCT
- 3:59THEREFORE WE CAN WRITE THIS AS A SUM OF NOT ONLY 2 LOGS
- 4:02BUT 3 LOGS INVOLVING X, Y, AND Z.
- 4:07SO THIS IS EQUAL TO NATURAL LOG X
- 4:12+ NATURAL LOG Y TO THE 3/2 + NATURAL LOG Z TO THE 5/2
- 4:23AND THEN FINALLY WE CAN APPLY
- 4:25THE POWER PROPERTY OF LOGARITHMS
- 4:27WHICH MEANS WE CAN TAKE THE EXPONENT HERE AND HERE
- 4:31AND MOVE IT TO THE FRONT SO IT'S THE COEFFICIENT.
- 4:36SO NOW WE HAVE NATURAL LOG X + 3/2 NATURAL LOG Y
- 4:44AND + 5/2 NATURAL LOG Z.
- 4:50AND NOW WE CAN PERFORM SUBSTITUTION ONCE AGAIN
- 4:52FOR NATURAL LOG X, NATURAL LOG Y, AND NATURAL LOG Z.
- 4:58NATURAL LOG X = 3 + 3/2 x NATURAL LOG Y, WHICH IS 4,
- 5:07WHICH I'LL WRITE AS 4/1 + 5/2 x NATURAL LOG Z
- 5:15WHERE NATURAL LOG Z = 5, WHICH I'LL WRITE AS 5/1.
- 5:21NOTICE HOW THIS PRODUCT HERE WILL SIMPLIFY.
- 5:24THERE'S ONE FACTOR OF 2 IN 2 AND 2 FACTORS OF 2 IN 4.
- 5:29NOTHING SIMPLIFIES HERE SO WE HAVE 3 + THIS WOULD BE 6,
- 5:38+ THIS WOULD BE 25/2 OR 12.5.
- 5:46SO 3 + 6 IS 9 AND 9 = 18/2.
- 5:5118/2 + 25/2 IS EQUAL TO 43/2 OR IF WE WANT 21.5.
- 6:14THAT'S GOING TO DO IT FOR THESE TWO EXAMPLES.
- 6:16I HOPE YOU FOUND THIS HELPFUL.
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