Add 4x²y,-2xy²,-5xy²,3x²y plz explain​

4x^2 - 2xy^2
5xy^2 +
3x^2y

12x^5y^4-2xy^2

This is so because 4+5+3 is 12, then using laws of indices to add your x and y you get x^5 and y^4

To simplify your answer to the lowest you have it in the form of
3x^2y^2(4x^2y - 2xy^2)

If you multiply this as well you get the same answer I got with the addition