<p>Hey guys,</p>
<p>I need help on this Grid-in question:</p>
<p>If 0 is less than or equal to x which is less than or equal to y and (x+y)^2-(x-y)^2 is greater than or equal to 25, what is the least possible value of y?</p>
<p>Thanks ahead of time,
Kevin</p>
<p>(x+y)^2-(x-y)^2 ≥ 25
difference of 2 squares:
((x+y)+(x-y))<em>((x+y)-(x-y)) ≥ 25
(2x)</em>(2y) ≥ 25
4xy ≥ 25
y ≥ x ≥ 0</p>
<p>if x is a big number, then y is also a big number because it is greater than or equal to it. So for y to be a small number, x also has to be a small number. For y to be the smallest possible number, it has to be equal to x. So you set x and y equal and solve for y</p>
<p>4y^2 ≥ 25
2y ≥ 5
y ≥ 2.5
y=2.5</p>