Inverse Laplace 7F5Bea
1. **State the problem:** Find the inverse Laplace transform of the function $$F(s) = \frac{s + 5}{s^2 - 2s - 3}$$.
2. **Factor the denominator:** The quadratic in the denominator factors as $$s^2 - 2s - 3 = (s - 3)(s + 1)$$.
3. **Set up partial fraction decomposition:** We express $$\frac{s + 5}{(s - 3)(s + 1)} = \frac{A}{s - 3} + \frac{B}{s + 1}$$.
4. **Multiply both sides by the denominator:**
$$s + 5 = A(s + 1) + B(s - 3)$$
5. **Expand and group terms:**
$$s + 5 = A s + A + B s - 3 B = (A + B) s + (A - 3 B)$$
6. **Equate coefficients:**
- Coefficient of $$s$$: $$1 = A + B$$
- Constant term: $$5 = A - 3 B$$
7. **Solve the system:**
From $$1 = A + B$$, we get $$A = 1 - B$$.
Substitute into $$5 = A - 3 B$$:
$$5 = (1 - B) - 3 B = 1 - 4 B$$
$$4 B = 1 - 5 = -4$$
$$B = -1$$
Then $$A = 1 - (-1) = 2$$.
8. **Rewrite the function:**
$$F(s) = \frac{2}{s - 3} - \frac{1}{s + 1}$$
9. **Recall inverse Laplace transforms:**
$$\mathcal{L}^{-1}\left\{ \frac{1}{s - a} \right\} = e^{a t}$$ for $$t \geq 0$$.
10. **Apply inverse Laplace transform:**
$$f(t) = 2 e^{3 t} - e^{-t}$$.
**Final answer:**
$$\boxed{f(t) = 2 e^{3 t} - e^{-t}}$$