因式分解 9x³y-7x²y²+2xy³=?

因式分解 9x³y-7x²y²+2xy³=?
因式分解 9x³y-7x²y²+2xy³=?

因式分解 9x³y-7x²y²+2xy³=?
9x³y-7x²y²+2xy³
=xy(9x²-7xy+2y²)
不能再分解下去了
若上面2xy³前面是-的话可以继续分
9x³y-7x²y²-2xy³
=xy(9x²-7xy-2y²)=xy(x-y)(9x+2y)

=xy(9x²-7xy+2y²)=xy(3x-y)(3x-2y)