Question

a² + b² = 29
a+b= -7
ab =?

Answer 1

$a+b=-7 \\ \\ (a+b)^2=(-7)^2 \\ \\ a^2+2ab+b^2=49 \\ \\ (a^2+b^2)+2ab=49 \\ \\ 29+2ab=49 \\ \\ 2ab=20 \\ \\ \boxed{ab=10}$