y^2+y-20

问题描述:

y^2+y-20
x^2-x-6
(x+2)(x-4)-7

y^2+y-20=(x+5)(x-4)
x^2-x-6=(x-3)(x+2)
(x+2)(x-4)-7=x^2-2x-8-7=x^2-2x-15=(x-5)(x+3)