How to express van der waals equation as virial expansion?

[Chaste]

Homework Statement

Express the van der Waals equation of state as a virial expansion in powers of
1/Vm and obtain expressions for B and C in terms of the parameters a and b.
(Hint. The expansion you will need is (1–x) -1 = 1+x+x2+... . Series expansions
are discussed in Appendix 2 of Atkins.)
Measurements on argon gave B=-21.7 cm3.mol-1 and C=1,200 cm6.mol-2 for the
virial coefficients at 273 K. What are the values of a and b in the corresponding
van der Waals equation of state?

Homework Equations

Van der waals equation of state : ( p + a / V^2 ) ( V-b ) = RT

The Attempt at a Solution

Apparently this question is very common and found throughout the web. But I couldn't find any solution. I don't even know how to begin with expressing ;(
please help. thanks.

 

[chrisk]

Solve for P giving you a term containing

$$\frac{1}{V_m-b}$$

Factor out V_m then use the hint.