The (r+1)th term: T_{r+1} = C(n, r) * x^{n-r} * y^r.

Critical point: The subscript is r+1, not r. So T_1 = C(n,0)*x^n, T_2 = C(n,1)*x^{n-1}*y, etc.

To find the coefficient of a specific power: write the general term, set the exponent of the variable to the required value, solve for r, and compute C(n,r).

For (ax^p + b/x^q)^n: T_{r+1} = C(n,r) * (ax^p)^{n-r} * (b/x^q)^r = C(n,r) * a^{n-r} * b^r * x^{p(n-r) - qr}.