Answer:
7m^5 - 3m^3 - 3
Explanation:
The first set of parentheses is unnecessary, so just remove them.
To remove the second set pf parentheses, since there is a negative sign to its left, change every sign inside the second set of parentheses. Then combine like terms.
(6m^5 + 3 - m^3 - 4m) - (-m^5 + 2m^3 - 4m + 6) =
= 6m^5 + 3 - m^3 - 4m + m^5 - 2m^3 + 4m - 6
= 7m^5 - 3m^3 - 3