(-5u^3v^4 + 9u) + (-5u^3v^4 - 8u + 8u^2v^2) + (-8u^4v^2 + 8u^3v^4)=

(-5u^3v^4 + 9u) + (-5u^3v^4 - 8u + 8u^2v^2) + (-8u^4v^2 + 8u^3v^4)=

=-5u^3v^4 + 9u+-5u^3v^4 - 8u + 8u^2v^2+-8u^4v^2 + 8u^3v^4

=-5u^3v^4+-5u^3v^4+ 8u^3v^4 + 9u- 8u + 8u^2v^2+-8u^4v^2

=-2u^3v^4+ 9u- 8u + 8u^2v^2+-8u^4v^2