x^2+px+q型的因式分解

题目

x^2+px+q型的因式分解
1.x^2+6x-72
2.x^2-3x-18
3.(x+y)^2-8(x+y)-48
4.x^4-7x^2-18
5.x^2-10xy-56y^2
给你们一个公式：x^2+(a+b)x+ab=(x+a)(x+b)

答案

1.x^2+6x-72 =(x-6)(x+12)2.x^2-3x-18 =(x-6)(x+3)3.(x+y)^2-8(x+y)-48 =(x+y-12)(x+y+4)4.x^4-7x^2-18 =(x^2+2)(x^2-9)=(x^2+2)(x+3)(x-3)5.x^2-10xy-56y^2 =(x-14y)(x+4y)