Question

find the product of 42,45 by ysing algebric identities.

Answer 1

42*45 = (40+2)(40+5)
(x+a)(x+b) = xsq + (a+b)x +ab
therefore, 40*40 + 2+5(40) + 2*5
1600+280+10
1890

Answer 2

(x+a)(x+b)= x^2+x(a+b)+ab

(40+2)(40+5) = 40^2+40(7)+10

= 1600+280+10

=1890