-25x^2+4因式分解（写步骤）
问题描述：
-25x^2+4因式分解（写步骤）
因式分解：-81+a^4 4（x+1）^2-9 （3x+2y）^2-(2x+3y)^2
x^2(a-1)+4(1-a)
答
-25x^2+4
=-(25x^2-4)
=-(5x+4)(5x-4)
-81+a^4
=a^4-81
=(a^2+9)(a^2-9)
=(a^2+9)(a+3)(a-3)
4(x+1)^2-9
=[2(x+1)+3]*[2(x+1)-3]
=(2x+5)(2x-1)
（3x+2y）^2-(2x+3y)^2
=[(3x+2y)+(2x+3y)]*[(3x+2y)-(2x+3y)]
=(5x+5y)(x-y)
=5(x+y)(x-y)
x^2(a-1)+4(1-a)
=x^2(a-1)-4(a-1)
=(a-1)(x^2-4)
=(a-1)(x+2)(x-2)