Math Question from the official SAT practice test (2007-08)

Test Preparation SAT Preparation
1

<p>So here is the question</p>

<ol>
<li>If 0≤x≤y and (x+y)² - (x-y)² ≥ 25, what is the least possible value of y?</li>
</ol>

<p>So here is what I have done so far but then I get stuck. I am hoping someone can guide me through the next step of this problem...</p>

<p>x²+2xy+y² - x²-2xy+y²≥ 25
4xy≥ 25
xy≥ 25/4</p>

<p>Now what do I do?</p>

2

<p>the least Y value is X ==> X*X>=25/4 ==> X >=5/2</p>

3

<p>You know x=y so…
(2x)^2-(0)2>25(or equal)
4x^2>25
X^2>25/4
X=5/2 and so does y. Check it and it works</p>