Question

(a+b+c+d)^2 求解求过程

Answer 1

原式=(a+b+c+d)²
=[(a+b)+(c+d)]²
=(a+b)²+(c+d)²+2(a+b)(c+d)
=a²+b²+2ab+c²+d²+2cd+2(ac+ad+bc+bd)
=a²+b²+c²+d²+2ab+2cd+2ac+2ad+2bc+2bd

Answer 2

(a+b+c+d)^2
=[(a+b)+(c+d)]²
=(a+b)²+2(a+b)(c+d)+(c+d)²
=(a²+2ab+b²)+2(ac+ad+bc+bd)+(c²+2cd+d²)
=a²+2ab+b²+2ac+2ad+2bc+2bd+c²+2cd+d²

Answer 3

(a+b+c+d)²
=[a+(b+c+d)]²
=a²+2a(b+c+d)+(b+c+d)²
=a²+2a(b+c+d)+[b+(c+d)]²
=a²+2a(b+c+d)+b²+2b(c+d)+c²+2cd+d²
=a²+b²+c²+d²+2ab+2ac+2ad+2bc+2bd+2cd