Question

Using (x + a) (x + b) = x² + (a + b) x + ab, evaluate 75 x 77

Answer 1

(x + a) (x + b) = x² + (a + b) x + ab

75 * 77=

=(70+5)(70+7)

=70²+(5+7)*70+5*7

=4900+12*70+35

=4900+840+35

=5775