2. When

is expanded as a series in ascending powers of x, the coefficients of x and

are -6 and 27 respectively.

a) Find the value of a and the value of n.

b) Find the coefficient of

.

c) State the set of values of x for which the expansion is valid.

I have attempted this question by trying to find simultaneous equations by comparing coefficients but I do not think it is the correct method since it seemed to be getting too complicated.

If someone could tell me whether i have done the first question correctly and show me how to do the second i would greatly appreciate it. Thanks in advance!