Question

Find the product by using the formula.

(7) 98 × 102

Answer 1

98 × 102
98 = 100 − 2
102 = 100 + 2
∴ 98 × 102 = (100 − 2) (100 + 2)
The expression (100 − 2) (100 + 2) is of the form (a + b) (a − b).
Thus, we can use the identity (a + b) (a − b) = a² − b² .
∴98 × 102 = (100 − 2) (100 + 2)
= (100)² − (2)²
= 10000 − 4
= 9996