SAT BB question

Test Preparation SAT Preparation
1

<p>I looked at the compiled list, and there are some questions not on there I have questions on
btw, this is not the 2nd edition bluebook, but the 1st</p>

<p>pg. 426 #14
If (a+b)^.5 = (a-b)^-.5, which of the following must be true
a) b = 0
b) a+b = 1
c) a-b = 1
d) a^2 + b^2 = 1
e) a^2 - b^2 = 1</p>

<p>I've read the answer posted and it said square both sides, but if square 1/2, wont i get 1/4? Can anyone explain this part?</p>

2

<p>the answer should be E. </p>

<p>(a+b)^.5 = sqrt(atb)
(a-b)^-.5 = 1/sqrt(a-b)</p>

<p>so we have</p>

<p>sqrt(a+b) = 1/sqrt(a-b)</p>

<p>isolate the 1</p>

<p>sqrt(a+b)*sqrt(a-b)=1</p>

<p>sqrt((a+b)(a-b))=1</p>

<p>square both sides</p>

<p>(atb)(a-b)=1</p>

<p>a^2-b^2=1</p>