Factories:
(l + m)2 - (l –m)2
We have,
(l + m)2 - (l –m)2
= {(l + m) + (l – m)}{(l + m) – (l – m)}
By using the formula a2 – b2 = (a + b)(a – b)
We get,
(l + m)2 - (l –m)2 = {(l + m) + (l – m)}{(l + m) – (l – m)}
= (l + m + l – m)(l + m – l + m)
= (2l)(2m)
= 4lm