Hello!

The solution should be 10/7, it's constant, therefor n must be equal to 5 => n = 5

Then we have

This is equal to

Now consider

=

=

In this case you only have to consider the x-terms with the biggest exponent (here it is x^5, this will tell you the limes)

Therefor the same problem is

=

=

and the solution should be 10/7, I guess you will be able to find c = 7