Oops, sorry for the typo in the title. :|

Need help with these please:

In the expansion of (1-ax)^n, the first three terms are 1-12x-63x^2. Find the values of a and n.

and

In the expansion of (x-(1/x^2))^8 find:

a) The term that has x^-1

b) The coefficient of the term that has x^2.

Just to make the second one a little clearer, here's something I whipped up with my MSPaint skills:

http://img529.imageshack.us/img529/7942/amtxu3.jpg