If (a - b) = 7 and ab = 9, then (a2 + b2) = ?
From the formula,
(a – b)2 = a2 + b2 –2ab
We get,
= a – b = 7 and ab = 9
By putting values, we get,
72 = a2 + b2 - 2× 9
= a2 + b2 = 49 + 18 = 67