Question

Find the product by using the formula.

(9) 57 × 63

Answer 1

57 × 63
57 = 60 − 3
63 = 60 + 3
∴ 57 × 63 = (60 − 3) (60 + 3)
The expression (60 − 3) (60 + 3) is of the form (a + b) (a − b).
Thus, we can use the identity (a + b) (a − b) = a² − b² .
∴ 57 × 63 = (60 − 3) (60 + 3)
= (60)² − (3)²
= 3600 − 9
= 3591