题目报错

题目：先化简，再求值：x²y-[2xy²-3(x²y-2xy²)]，其中 x=1，y=-2。

答案：原式 = x²y-[2xy²-3x²y+6xy²] = x²y-2xy²+3x²y-6xy² = (x²y+3x²y)+(-2xy²-6xy²) = 4x²y-8xy²。当 x=1，y=-2 时： 4×1×(-2)-8×1×4 = -8-32 = -40。