Question

Find the values of the following using the formula of the square of a binomial.

(4) 78²

Answer 1

78²
or 78 = 80 − 2
78² = (80 − 2)²
Thus, we can use the identity (a − b)² = a² − 2ab + b² .
∴ 78² = (80 − 2)²
= (80)² − 2 (80) (2) + (2)²
= 6400 − 320 + 4
= 6400 + 4 − 320
= 6404 − 320
= 6084