Question

consider the expansion (y+4)^9. whats the exponent of the y in the 10th term.

how do i solve this?

Answer 1

What you will notice about the expansion is that the exponent for y will start at nine and decrease by 1 at each term. Thus, the exponent for the tenth term must be zero.

Answer 2

if you want to learn more about binomial expansion, you should check out http://en.wikipedia.org/wiki/Pascal's_triangle

it shows the coefficients for the expansion of any binomial to any power that is a positive integer