Question

use formula (a+b)(a-b) =a^+b^) to evaluate 21*19​

Answer 1

(19+2)(19-2)=(19)^2-(2)^2

hope this helps u.

Answer 2

21×19

=(20+1)(20-1)

=(20)^2 - (1)^2

=400-1

=399

Hope it helps...

Regards,

Leukonov/Olegion.