x²-4x-9996=0
(x-102)(x+98)=0
x=102或 x=-98
y(x-y)²-（y-x)^3
=y(x-y)²+（x-y)^3
=(x-y)²(y+x-y)
=x(x-y)²
x^n+2-x^n+1-2x^n
=x^n(x²-x-2)
=x^n (x-2)(x+1)
x²-xy+2yz-4z²
=x²-4z²-xy+2yz
=(x+2z)(z-2z)-y(x-2z)
=(x-2z)(x+2z-y)
x²-2xy+y²-9
=(x-y)²-9
=(x-y+3)(x-y-3)问一下：x平方-4x-9996