- 4y – 7y² – 2y ² – 7 x 3 – 4y² + y²

-7x^3 -12y^2-4y

Explanation:

The -7x^3 is alone so you don't have to worry about adding or subtracting it. You add -7y^2-2y^2-4y^2+y^2 together then you just put the -4y because it's alone.

not sure if this is what you'r looking for eubacteria and archaebacteria