Solving we get, .

 

The expression on the right represents the cube roots of unity represented by 1,and .

 

Hence,

  
Now we employ method of partial fractions to obtain,

 

Compare the coefficients to get,

and .

Solve, u'll get and .

 

So the integral now becomes,

 

Substitute . So that  and  .

 

.

 

 

The above two integrals are of standard form and can be solved quite easily!