Answer:
4m - 31
-------------------
(m+9)(m-9)
Explanation:
1) the given sum is:
4 5
------ + -------------
m+9 m^2 - 81
2) factor m^2 - 81
m^2 - 81 = (m + 9)(m - 9)
3) rewrite the sum
4 5
------- + ------------------
m+9 (m+9)(m-9)
4) least common denominator: (m + 9)(m - 9)
4(m-9) + 5 4m - 36 + 5 4m - 31
--------------------- = ------------------- = ----------------
(m+9)(m-9) (m+9)(m-9) (m+9)(m-9)
