Browse · MATH Print → jmc algebra intermediate Problem If (x+y)2=1 and xy=−4, what is the value of x2+y2? Solution — click to reveal We see that (x+y)2=(x2+y2)+2xy=1. We want to find x2+y2 and are given xy=−4. So, x2+y2+2xy=x2+y2+2(−4)=1. It follows that x2+y2=9. ← Previous problem Next problem →