I am taking Gr 12 Data Management online and am really struggling to understand this chapter. One of the questions is:

The first three terms in the expansion of (1+ay)^n are 1, 12y, and 68y^2. Evaluate a and n. Use the fact that

(1+ay)^n=1+nay+(n(n-1)/2)(ay)^2+...

I have gone over my notes and the text and dont know how go about evaluating for a and n. Any help would be greatly appreciated! Thanks in advance