X减Y等于3,XY=1,求(负2XY加2X加3Y)减(3XY加2Y减2X)减(X加4Y加XY)的值

问题描述:

X减Y等于3,XY=1,求(负2XY加2X加3Y)减(3XY加2Y减2X)减(X加4Y加XY)的值

=-2xy+2x+3y-3xy-2y+2x-x-4y-xy
=-6xy+3x-3y
=-6xy+3(x-y)
=-6+9
=3