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

18