數學問題？請幫忙

(a＋b)^2
= (a + b) x (a + b)
= a^2 + ab + ab + b^2
= a^2 + 2ab + b^2

2009-07-11 11:50:23 補充：
(a＋b)^2
= (a + b) x (a + b)
= a x (a + b) + b x (a + b)
= a^2 + ab + ab + b^2
= a^2 + 2ab + b^2

(a+b)^2
=(a+b)(a+b)
=a(a+b)+b(a+b)
=a^2+ab+ab+b^2
=a^2+2ab+b^2(這是公式,必記)

這條數的答案是:
(a＋b)^2＝
a^2+2ab+b^2

用恆等式:
(a+b)^2 = a^2+2ab+b^2