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SAT Math 2.2 Algebra and Functions 298 Views
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Description:
SAT Math 2.2 Algebra and Functions. What value of y is correct?
Transcript
- 00:02
Put this in your calculator and shmoop it...
- 00:05
If x to the y power... to the y power... to the y power...
- 00:10
to the y power... equals x to the 81st power... then y can be which of the following?
- 00:17
And here are the potential answers...
- 00:23
There may be a lot of parentheses here, but don't panic.
Full Transcript
- 00:25
All we need is a simple exponent rule. Remember this rule?
- 00:31
When we take an exponent to an exponent, all we have to do is multiply the two exponents together.
- 00:38
So x to the y to the y is the same thing as x to the y squared.
- 00:44
So x to the y squared to the y to the y is the same thing as x to the y to the fourth power.
- 00:53
The base of both sides are the same, so the exponents of both sides must be the same.
- 01:00
Yeah, probably.
- 01:01
So y to the fourth is equal to 81.
- 01:03
What number, to the fourth power, is 81?
- 01:06
Well, 3 times 3 is 9 times 3 is 27 times 3 is 81, but
- 01:10
3 isn't the only number that's equals 81 when raised
- 01:14
to the fourth power. What's another one that works?
- 01:18
Negative 3 to the fourth power is also 81.
- 01:21
The negative cancels out since the exponent is even.
- 01:25
So yep, E is our answer.
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