Question

evaluate 78×82 by using identities.

Answer 1

78 × 82

= ( 80 - 2 )( 80 + 2 )

using formula --

( a - b ) ( a + b ) = a² - b ²

we get --

80² - 4

= 6400 - 4

= 6496 Ans..

Answer 2

$(80 - 2) (80 + 2) \\ = (80) ^{2} - (2) ^{2} \\ = 6400 - 4 \\ = 6396$
I hope it is the answer