Question

If a^2+b^2=5 and a+b=3, then ab=

Answer 1

ab = 2

Explanation:

You know that ...

(a +b)^2 = a^2 +2ab +b^2

Rearranging, we can solve for ab ...

2ab = (a^2 +b^2) -(a +b)^2

ab = ((a +b)^2 -(a^2 +b^2))/2 = (3^2 -5)/2

ab = 2