Question

X^2Y-[-X^2Y+(XYZ-X^2Z)+XYZ]-X^2Z,其中x=-1,y=-2,z=1/3

Answer 1

X^2-[-X^2Y+(XYZ-X^2Z)+XYZ]-X^2Z

=x^2-[-x^2y+xyz-x^2z+xyz]-x^2z

=x^2+x^2z-2xyz

当x=-1,y=-2,z=1/3时

原式=1+1/3-4/3=0