3n-5 20th term
Well ....if we have (3n - 5)^20, the 20th term is just C(20,20)(3n)^0(-5)^20 = 1*1*95367431640625 = 95367431640625
If (3n - 5) is raised to a greater power, we would need to know what that power might be before an answer could be given........
