If ∑n=0∞anxn\sum_{n=0}^{\infty} a_n x^n∑n=0∞anxn converges to f(x)=x1−x−x2f(x) = \frac{x}{1-x-x^2}f(x)=1−x−x2x for ∣x∣<5−12|x| < \frac{\sqrt{5}-1}{2}∣x∣<25−1, find a4a_4a4.
a4=2a_4 = 2a4=2
a4=3a_4 = 3a4=3
a4=4a_4 = 4a4=4
a4=5a_4 = 5a4=5