Question:
Factorise:
(l + m)2 − (l − m)2
Solution:
We have:
$(l+m)^{2}-(l-m)^{2}=\{(l+m)+(l-m)\}\{(l+m)-(l-m)\}$
$=(l+m+l-m)(l+m-l+m)$
$=(2 l)(2 m)$
$\therefore(l+m)^{2}-(l-m)^{2}=(2 l)(2 m)$
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