Question

化简求值：3x²y-[2x²y-(2xyz-x²z)-4x²z]-xyz，其中x=2，y=-3，z=1。

Answer 1

解：3x²y-[2x²y-(2xyz-x²z)-4x²z]-xyz
     =3x²y-[2x²y-2xyz+x²z-4x²z]-xyz
     =3x²y-2x²y+2xyz-x²z+4x²z-xyz
     =x²y+xyz+3x²z
   当x=2，y=-3，z=1时，
  原式=2²×(-3)+2×(-3)×1+3×2²×1
         =-12-6+12
         =-6