2x的平方-6xy-8y的平方
=2x²-6xy-8y²
=(2x+2)(x-4)
=2(x+1)(z-4)
-9x的平方+9xy+10y的平方
=-9x²+9xy+10y²
=-(9x²-9xy-10y²)
=-(3x-5y)(3x+2y)O(∩_∩)O谢谢