Question

Without actual squaring, find the value of
(a) 685square - 684square​

Answer 1

We know that, (a^2 - b^2) = (a+b)(a-b)

Similarly,

(685^2 - 684^2) = (685+684)(685-684)

= (1369)(1)

= 1369

Hence, (685^2 - 684^2) = 1369