Question

已知2x-3=0,3y+2=0,求代数式x(y2-2)+3xy-y(2x2+5)-9的值

Answer 1

2x-3=0得x=3/2，3y+2=0得y=-2/3
然后直接代
x(y2-2)+3xy-y(2x2+5)-9=-8

Answer 2

2x=3
3y=-2
xy=-1
所以有：
x(y2-2)+3xy-y(2x2+5)-9
=xy*y-2x+3*xy-xy*2x-5y-9
=(-1)*y-3+3*(-1)-(-1)*3-5y-9
=-6y-12
=-2*(-2)-12
=-8