(3/2)X^2YZ+3XY^2Z-(9/2)XYZ^2
=XYZ[(3/2)X+3Y-(9/2)Z]
=XYZ[(3X+6Y-9Z)/2]
=XYZ[3(X+2Y-3Z)/2]
=2*[3*(-1/3)/2]
=-1