If (x+y)^2 = 45 and xy=8, what is the value of (x-y)^2?
(x + y)^2 = 45
x^2 + y^2 + 2xy = 45
x^2 + y^2 + 2(8) = 45
x^2 + y^2 = 29
(x-y)^2 = x^2 + y^2 -2xy
[x^2 + y^2] - 2xy =
[29] -16 = 13
