3x²y-[2xz-（2xyz-xz）-2x²y]-2xyz,急3x²y-[2xz-（2xyz-xz）-2x²y]-2xyz,先化简再求值.其中x=-2,y=-3,z=4、

Question

3x²y-[2xz-（2xyz-xz）-2x²y]-2xyz,急
3x²y-[2xz-（2xyz-xz）-2x²y]-2xyz,先化简再求值.其中x=-2,y=-3,z=4、

Answer 1

原式=3x²y-(2xz-2xyz+xz-2x²y)-2xyz
=3x²y-2xy+2xyz-xz+2x²y-2xyz
=(3x²y+2x²y)+(-2xz-xz)+(2xyz-2xyz)
=5x²y-3xz
当x=-2, y=-3, z=4时
原式=5×(-2)²×(-3)-3×(-2)×4
=5×4×(-3)-[-(3×2×4)]
=-(5×4×3)-(-24)
=-60+24
=-(60-24)
= -36