<p>Hi.. all.. can somebody explain to me how to do #12 on page 656.. thanks...</p>
<p>hello.. doesnt anybody know this..</p>
<p>k ill take a shot at this,
the distance from P to S is 2
the perimeter is 10
x= length
2x+2(2)=10
x=3
anyway, if we know the length (vertical distance) is 3 then point R is at (1,3)
then substitute that into the equation y=ax^2
3=a x 1^2 so a = 3
yeah so..not sure if i'm right though, but it makes sense to me</p>
<p>Since PQRS is a rectangle, PS = QR = 1- (-1) = 2. Therefore, PQ + QR = 2 + 2 = 4, and since the perimeter is 10, we know what's left over (PQ + RS) = 10 - 4 = 6 and that RS = PQ = 6/2 = 3. Hence, the y-values for R and Q are 3 => plugging it back into the formula b/c R and Q are on the function => 3 = ax^2. Since x = 1 or -1 (it doesn't make a difference b/c it's x^2), we have 3 = a(1)^2 => a = 3.</p>