先化简再求值3xyz+2(x^2y+y^2z-xyz)-xyz+2z^2x x=1 y= -1 z=2

问题描述:

先化简再求值3xyz+2(x^2y+y^2z-xyz)-xyz+2z^2x x=1 y= -1 z=2

3xyz+2(x^2y+y^2z-xyz)-xyz+2z^2x
原式= 3xyz+2(x²y+y²z+z²x)-3xyz
=2(x²y+y²z+z²x)
=2×(-1+2+4)
=2×5
=10