初等数学常用公式(共13页).doc

精选优质文档-倾情为你奉上初等数学常用公式：（一）代数乘法及因式分解公式（1）(1) (x+a) (x+b) =x2 + (a+b)x +ab (2) (ab)2=a2 2ab+b2 (3) (ab)3=a33a2b+3ab2b3 (4) (a+b+c)2=a2+b2+c2+2ab+2bc+2ca (5) (a+b+c)3=a3+b3+c3+3a2b+3ab2+3b2c+3bc2+ 3a2c+ 3ac2+ 6abc (6) a2-b2=(a -b)(a+b) (7) a3b3= (ab) (a2ab +b2). (8) an-bn= (a-b)(an-1 +an-2b+an-3b2 +abn-2+bn-1) (n为正整数) (9) an-bn= (a+b)(an-1-an-2b+an-3b2-+abn-2-bn-1) (n为偶数) (10) an+bn=(a+b)(an-1-an-2b+an-3b2-abn-2+bn-1