Question

3x平方y-[3x平方yz-（2xyz-x平方z）-4x平方z]-2xy，其中x=-2，y=-3，z=1

Answer 1

3x平方y-[3x平方yz-（2xyz-x平方z）-4x平方z]-2xy
=3x²y-3x²yz+2xyz-x²z+4x²z-2xy
=3x²y(1-z)+2xy(z-1)+3x²z
=3x²z
=3*4
=12

Answer 2

3x平方y-[3x平方yz-（2xyz-x平方z）-4x平方z]-2xy
=3x^2y-[3x^2yz-2xyz+x^2z-4x^2z]-2xy
=3x^2y-3x^2yz+2xyz-x^2z+4x^2z-2xy
=3x^2y-3x^2yz+2xyz+3x^2z-2xy
z=1
上式=3x^2y-3x^2y+2xy+3x^2-2xy
=3x^2
=3*(-2)^2
=12