4x^2y-[2xy-3(xy-x)+4x^2y] 先化簡,再求值,其中x=1/3,y=3/4

題目：

4x^2y-[2xy-3(xy-x)+4x^2y] 先化簡,再求值,其中x=1/3,y=3/4

解答：

化簡得=4x^2y-[2xy-3xy+3x+4x^2y]
=4x^2y-2xy+3xy-3x-4x^2y
=xy-3x
當x=1/3,y=3/4時,xy-3x=1/4-1=-3/4