Answer:
8m^4 -8m^3 -7m^2 -12 m
Explanation:
(4m^4 - 8m^3 - 7m) + (4m^4 - 7m^2 - 5m)
I like to line them up vertically. I put 0 in the spots to keep them lined up
4m^4 - 8m^3 +0m^2 -7m
+4m^4 +0m^3 - 7m^2 - 5m
--------------------------------------------
8m^4 -8m^3 -7m^2 -12 m