5a . (- 1/5 a)=
2/3 x^2 . 1/4 xy=
-5x . (-5 xy)=
-8xy - 8x - 2xy=
5xy + 4x -7xy=
4 x^3 y . 2 x=
9 x^2 + 5 x^2 + 3 - x=
- a^2
8 x^4 y
25 x^2 y
-10 xy - 8x
14 x^2 - x + 3
-2xy + 4x
2/12 x^3 y