3x²y+xy²-[2xy²-4x²y+（x²y-2xy²）],计算步骤是什么

3x²y+xy²-[2xy²-4x²y+（x²y-2xy²）],计算步骤是什么
3x²y+xy²-[2xy²-4x²y+（x²y-2xy²）],计算步骤是什么

3x²y+xy²-[2xy²-4x²y+（x²y-2xy²）],计算步骤是什么
先去括号得3x^2y+xy^2-2xy^2+4x^2y-x^2y+2xy^2
合并同类项得6x^2y+xy^2

这是要干嘛?化简?

原式=3x²y+xy²-(2xy²-4x²y+x²y-2xy²)
=3x²y+xy²-(-3x²y)
=3x²y+xy²+3x²y
=6x²y+xy²