Find the inverse Laplace transform $f(t) = {\mathcal L}^{-1} \left\lbrace F(s) \right\rbrace$ of the function $\displaystyle F(s) = \frac{s}{s^{2}+64}-\frac{6}{s^{2}+4}$.

$\displaystyle f(t) = {\mathcal L}^{-1} \left\lbrace \frac{s}{s^{2}+64}-\frac{6}{s^{2}+4} \right\rbrace =$ help (formulas)