Question

Determine the coefficient of the 3rd term in the expansion of (x+2y)^7.

I tried using the formula,nCk (a^(n-k)) ((b)^k), but it doesn't indicate what n is.

Answer 1

It depends upon how they do the numbering. I would assume that the x^7 term is the first and the x^5 y^2 term is the third. In that case, n=7 and k = 2