Question

$({a + b + c + d} )^{2}$

Answer 1

$(a +b + c + d)^{2}$
=(a+b+c+d)(a+b+c+d)
=$a^{2}$+ab+ac+ad+ab+$b^{2}$+bc+bd+ac+bc+$c^{2}$+cd+ad+bd+cd+$d ^{2}$
=$a^{2}$+$b^{2}$+$c^{2}$+$d ^{2}$+2ab+2bc+2cd+2da