If x+y=9 and xy=10, what is the value of \(x^2 + y^2\)?
x^2 + y^2 = 72.
Note that \(x^2+y^2=(x+y)^2-2xy\)
Substituting what we know, we have: \(x^2+y^2=9^2-2 \times 10\)
Solving this, we find: \(x^2+y^2=\color{brown}\boxed{61}\)
+2668 
