Answer
$9x^4+9x^5+9x^6+9x^7...+9x^{n+4}...$
Work Step by Step
We are given $f(x)=\frac{9x^{4}}{1-x}$
with $c=9x^4$ for $r$ in $(-1,1)$
The Taylor series for $f(x)=\frac{9x^{4}}{1-x}$ is
$f(x)=9x^4+9x^4.x+9x^4.x^2+9x^4.x^3+...9x^4x^n+...$
$=9x^4+9x^5+9x^6+9x^7...+9x^{n+4}...$
