how to find inverse?

Test Preparation SAT Preparation
1

<p>hi i am taking a sat prep course and i was given this problem</p>

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<p>can someone please explain how to solve this?</p>

<p>many thanks</p>

2

<p>if my math is rit, its C
1st - switch X and Y
x=2y/y-1
x(y-1)=2y
xy-x=2y
xy-2y=x
y(x-2)=x
y=x/x-2 -----> Answer</p>

3

<p>thank you i think you are correct
also sorry for asking again but </p>

<p>how exactly do i do</p>

<p>log(z)-log(4)=2 (solve for z)</p>

<p>where can i get started?</p>

4

<p>Amandeep1: this could be interesting because I don’t have my calculator with me right now. I might be able to walk you through it, but you are going to have to do the calculations!</p>

<p>When dealing with logs,subtraction indicates division. So:</p>

<p>log(z) - log(4) = log(z)/log(4)
log(z)/log(4) = 2
log(z) = 2log(4)
log (z) = (the solution to 2log(4))
When there is no base indicated, a base of 10 is inferred. So:
log “base 10” of z = the solution to 2log(4)
10^the solution should (hypothetically) = z </p>

<p>And you can always check your answer by plugging it into the original equation.</p>

<p>I haven’t done precalc/algebra II since school let out. I am a little rusty, but see if the above works!!</p>

5

<p>log(z)-log(4)=2
log(z)=2 + log(4)
[2nd] LOG of (2 + log(4)) = 400
u can check by doing log(400) - log(4) = 2</p>

6

<p>Hmmm…</p>

<p>When I condensed the original problem to the inferred division problem, my method gives the right answer when I plugged my answer back into the division problem. could someone tell me if I am doing this right or not?</p>

7

<p>Both questions are beyond the SAT Reasoning test scope - they belong to the SAT Subject Math test.
log(z)-log(4) = log(z/4), so
log(z/4) = 2
10^log(z/4) = 10^2
z/4 = 100
z = 400</p>

8

<p>ivy, I got the answer of 16 using ur method…that is wrong cuz
log(16)-log(4) = .602059913</p>

<p>reason:
log(z) - log(4) = log(z)/log(4) —> wrong b/c it is log(z) - log(4) = log(z/4)</p>

<p>using that method:</p>

<p>log(z) - log(4) = log(z/4)
log(z/4) = 2
10^(2) = 100
(but since its z/4)
z=100 x 4
z=400</p>

<p>both methods give u the write answer</p>

9

<p>Thanks! Other than being rusty, I know there was a reason I got a B in PreCalc!!</p>

10

<p>thanks for the help everyone</p>