Question

先化简,再求值:5x^2y-[4xy^2-3(2xyz-2x^y)]+4(xy^2-xyz),

Answer 1

即x+2=y-4=0

x=-2,y=4

z=-1

所以原式=5x^2y-4xy^2+3(2xyz-2x^y)+4xy^2-4xyz

=5x^2y+6xyz-6x^y-4xyz

=-5x^2y+2xyz

=-5*4*4+2*（-2）*4*（-1）

=-80+16

=-64