k + 1 k x + 2*x - x - 2
x^(k + 1) + 2*x^k - x - 1*2
-2.0 + x^(1.0 + k) - x + 2.0*x^k
/ k\ \-1 + x /*(2 + x)
(-1 + x^k)*(2 + x)
k k -2 - x + 2*x + x*x
-2 - x + 2*x^k + x*x^k