Q1)Find, in its simplest form, the coefficient of in the expansion, in ascending powers of , of

Q2) Expand as a series of ascending powers of up to and including the term in , Simplify the coefficients.

I got the above part right and derived at the answer of

However, its the following part that i dont get

In The expansion of , where is a constant, the coefficient of is zero. By writing as , or otherwise, find the value of k.

Any help is appreciated ^^