(3x²y-xy²)-3(x²y-2xy²) x=2分之1 y=3分之1(3x²y-xy²)-3(x²y-2xy²) x=2分之1 y=3分之1

问题描述:

(3x²y-xy²)-3(x²y-2xy²) x=2分之1 y=3分之1
(3x²y-xy²)-3(x²y-2xy²) x=2分之1 y=3分之1

可以先分解因式
(3x²y-xy²)-3(x²y-2xy²)
=xy(3x-y)-xy(3x-6y)
=xy(3x-y-3x+6y)
=5xy²
把x=2分之1 y=3分之1代入
5xy²=5 *1/2 *(1/3)²=5/18