If $x + y =2$ and $xy = 23$, then what is $x^2 + y^2$?
x + y = 2 square both sides
x^2 + 2xy + y^2 = 4
x^2 + 2(23) + y^2 = 4
x^2 + 46 + y^2 = 4 subtract 46 from both sides
x^2 + y^2 = -44
