Evaluate 396

^{2}– 386^{2}

__Solution__
We apply difference of two squares:
a

^{2}- b^{2}= (a+b)(a-b)
396

^{2}– 386^{2 }= (396 + 386)( 396 – 386)
=
(782)( 10)

=
7820 [only add a zero at 782]

396

^{2}– 386^{2 }= 13820

__TRY THIS…………….__
Evaluate 508

^{2}– 408^{2}