Question

89×89 without actual multiplications

Answer 1

89 × 89

Can also be written as –

= ( 89 )²

= ( 90 - 1 )²

Using identity –

$<b>( a - b )² = a² + b² - 2ab</b>$

Here, a = 90, b = 1

= ( 90 )² + ( 1 )² + 2 ( 90 ) ( 1 )

= 8100 + 1 - 180

= 8101 - 180

= $<b>7921</b>$