因式分解(3道)用“十字相乘法”x^3-5x^2y-24xy^2x^3-3x^2-10x(x^2+4x)^2-x^2-4x-20
问题描述:
因式分解(3道)
用“十字相乘法”
x^3-5x^2y-24xy^2
x^3-3x^2-10x
(x^2+4x)^2-x^2-4x-20
答
1.=x(x-8y)(x+3y)
2.=x(x-5)(x+2)
3.=(x^2+4x-5)(x^2+4x+4)
=(x+5)(x-1)(x+2)^2
答
x^3-5x^2y-24xy^2 =x(x^2-5xy-24y^2)=x(x-8y)(x+3y)x^3-3x^2-10x =x(x^2-3x-10)=x(x-5)(x+2)(x^2+4x)^2-x^2-4x-20=(x^2+4x)^2-(x^2+4x)-20=(x^2+4x-5)(x^2+4x+4)=(x+5)(x-1)(x+2)^2