Question 37698
For the equation {{{m^3-n^3}}}
You may have made a careless mistake in your answer. 
If you expand the equation you gave, the first term would be {{{c^4}}} because you have {{{c^3*c}}}.
The correct answer is:
{{{(m-n)(m^2+mn+n^2)}}}

For the second equation {{{c^3+f^3}}}
Your answer has a tiny common error. 
You also made the same error as above. 
The first part is correct. {{{(c+f)}}}
You should know that whenever you square a negative number, it beccomes positive.
The correct answer is:
{{{(c+f)(c^2-cf+f^2)}}}

Hope this helps!