因式分解(1)9a的平方-b的平方+2b-1 (2)x^3+3x^2-4x-12 (3)1/4a^3+1/3a^2b+1/9ab
问题描述：
因式分解(1)9a的平方-b的平方+2b-1 (2)x^3+3x^2-4x-12 (3)1/4a^3+1/3a^2b+1/9ab
答
(1)9a的平方-b的平方+2b-1 =(3a)²-(b-1)²=(3a+b-1)(3a-b+1)(2)x^3+3x^2-4x-12 =x²(x+3)-4(x+3)=(x²-4)(x+3)=(x+2)(x-2)(x+3)(3)1/4a^3+1/3a^2b+1/9ab²=a[(1/2a)²+2×(1/2a)×(1/3b)+(...