Using suitable identities, evaluate the following : 1. 103^2 2. 72 × 68

Question

Using suitable identities, evaluate the following :

1. 103²
2. 72 × 68

Answer 1

1. 103²

We know (a+b)² = a² + b² + 2ab

Using this identity, we get 

103² = (100 + 3)²

= 100² + 3² + 2 × 100 × 3

= 10000 + 9 + 600

= 10609

2. 72 × 68

= (70 + 2) (70 - 2)

Using identity (a-b) (a+b) = a² - b²

= (70)² - (2)²

= 4900 - 4

= 4896