Hi guys!

I have a homework question about the binomial expansion:

The first four terms, in ascending powers of x, of the binomial expansion of (1+kx)^n are

1 + Ax + Bx^2 + Bx^3 + ...

where k is a positive constant and A, B and n are positive integers.

a) By considering the coefficients of x^2 and x^3, show that 3=(n-2)k

Any help would be really great

Thanks in advance!