If a - b = 3 and a² + b² = 29, find the value of ab = ?

A. 10

B. 12

C. 15

D. 18

Answer: Option A

Solution(By Examveda Team)

$$\eqalign{ & 2ab \cr & = \left( {{a^2} + {b^2}} \right) - {\left( {a - b} \right)^2} \cr & = 29 - 9 = 20 \cr & \therefore ab = 10 \cr} $$