7a + 5a + 3a=
17x ^2 - 4x ^2=
2x + 3x =
-4ab + 2ab =
-5x^2 y^2 z - (-x^2 y^2 z)=
2xy - 2x + 2y=
2xy + 4xy - 8xy=
5x^4 - 2x^2 - 3x^2=
13x^2
-2ab
15a
5x^4 - 5x^2
-4x^2 y^2 z
2xy - 2x + 2y
-2xy
5x
