Really Hard Math Problem?

[Roflcopter]

Let ABC be a triangle such that angle ACB = Pi/6 [ :D no idea how to insert the image] and let a,b and c denote the lengths of the sides opposite to A,B and C respectively. The value of x for which a= x^2+x+1,b=x^2-1 and c=2x+1 is ..

Hint: use the cosine law rearranged into cos C = (a^2+b^2-c^2)/(2ab). We know angle C and we know a, b and c. This will give us a quadratic equation in R[x] with only one viable root (the other is negative).