Question Number 138477 by mathlove last updated on 14/Apr/21
Answered by Ñï= last updated on 14/Apr/21
$${a}^{\mathrm{2}} +\mathrm{2}{ab}+{b}^{\mathrm{2}} −{d}^{\mathrm{2}} −\mathrm{2}{cd}−{c}^{\mathrm{2}} \\ $$$$=\left({a}+{b}\right)^{\mathrm{2}} −\left({c}+{d}\right)^{\mathrm{2}} \\ $$$$=\left({a}+{b}+{c}+{d}\right)\left({a}+{b}−{c}−{d}\right) \\ $$