$\displaystyle \frac{s}{s^{2}-12s+36} =$

$\hskip 20pt s$ --------------------- $\big( s-$$\big)^2$

$\displaystyle \frac{s}{s^{2}-12s+36} = F\Big\vert_{s - 6}$ where $F(s) =$

Therefore $f(t) =$