I am having trouble finding the inverse Laplace transform of:

$\frac{1}{{s}^{2}-9s+20}$

I tried writing it in a different way:

$L}^{-1}\left\{\frac{1}{{(s-\frac{9}{2})}^{2}-{\left(\frac{1}{2}\right)}^{2}}\right\}=2{L}^{-1}\left\{\frac{\frac{1}{2}}{{(s-\frac{9}{2})}^{2}-{\left(\frac{1}{2}\right)}^{2}}\right\$

I tried writing it in a different way: