Question

If a-b = 7 and ab = 9, then a^2 + b^2 = ?

Answer 1

a-b=7
ab=9
a^2 +b^2 = (a-b) ^2 +2ab
Or, a^2 +b^2 =7^2 +2(9) [putting the value]
Or, a^2 +b^2 =49+18
So a^2 +b^2 =67