Find the middle term of the binomial expansion of (3a-b)^10

Question

anonymous · Answer

n+1 terms, so 11 terms. 6th term, I guess

anonymous · Answer

I know the answer, but I was wondering if there was a method to solve it without guessing/inferring what the i-1 of $$\left(\begin{matrix}n \ i-1\end{matrix}\right) a ^{n-(i-1)} b ^{i-1}$$
is.

anonymous · Answer

I copied it verbatim from my textbook o-o

anonymous · Answer

if you substitute i-1 with k, it's right. Mine formula is just so that i can equal the nth term. Your n(th term) would need to be decreased by 1. Just technicalities.

anonymous · Answer

errr nevermind. I chose a bad example. You just substitute the given values in this one.