Determine the coefficient of xnx^nxn in the power series expansion of f(x)=11−x−2x2f(x) = \frac{1}{1-x-2x^2}f(x)=1−x−2x21.
2n+1−(−1)n+13\frac{2^{n+1} - (-1)^{n+1}}{3}32n+1−(−1)n+1
2n+(−1)n3\frac{2^n + (-1)^n}{3}32n+(−1)n
2n+1+(−1)n3\frac{2^{n+1} + (-1)^n}{3}32n+1+(−1)n
2n−(−1)n3\frac{2^n - (-1)^n}{3}32n−(−1)n