1. **State the problem:** Solve the initial value problem $$y'' - 6y' + 5y = 3e^{2t}$$ with initial conditions $$y(0) = 2$$ and $$y'(0) = 3$$ using the Laplace transform method.
2. **Recall the Laplace transform formulas:**
- $$\mathcal{L}\{y''\} = s^2Y(s) - sy(0) - y'(0)$$
- $$\mathcal{L}\{y'\} = sY(s) - y(0)$$
- $$\mathcal{L}\{y\} = Y(s)$$
- $$\mathcal{L}\{e^{at}\} = \frac{1}{s - a}$$ for $$s > a$$.
3. **Apply Laplace transform to both sides:**
$$\mathcal{L}\{y'' - 6y' + 5y\} = \mathcal{L}\{3e^{2t}\}$$
Using linearity:
$$s^2Y(s) - sy(0) - y'(0) - 6(sY(s) - y(0)) + 5Y(s) = \frac{3}{s - 2}$$
Substitute initial values $$y(0) = 2$$ and $$y'(0) = 3$$:
$$s^2Y(s) - 2s - 3 - 6sY(s) + 12 + 5Y(s) = \frac{3}{s - 2}$$
4. **Group terms:**
$$\left(s^2 - 6s + 5\right)Y(s) - 2s - 3 + 12 = \frac{3}{s - 2}$$
Simplify constants:
$$\left(s^2 - 6s + 5\right)Y(s) + (-2s + 9) = \frac{3}{s - 2}$$
5. **Isolate $$Y(s)$$:**
$$Y(s) = \frac{3}{(s - 2)(s^2 - 6s + 5)} + \frac{2s - 9}{s^2 - 6s + 5}$$
6. **Factor quadratic:**
$$s^2 - 6s + 5 = (s - 1)(s - 5)$$
Rewrite:
$$Y(s) = \frac{3}{(s - 2)(s - 1)(s - 5)} + \frac{2s - 9}{(s - 1)(s - 5)}$$
7. **Partial fraction decomposition:**
Decompose $$\frac{3}{(s - 2)(s - 1)(s - 5)} = \frac{A}{s - 2} + \frac{B}{s - 1} + \frac{C}{s - 5}$$
Multiply both sides by denominator:
$$3 = A(s - 1)(s - 5) + B(s - 2)(s - 5) + C(s - 2)(s - 1)$$
Plug in $$s=2$$:
$$3 = A(2 - 1)(2 - 5) = A(1)(-3) = -3A \Rightarrow A = -1$$
Plug in $$s=1$$:
$$3 = B(1 - 2)(1 - 5) = B(-1)(-4) = 4B \Rightarrow B = \frac{3}{4}$$
Plug in $$s=5$$:
$$3 = C(5 - 2)(5 - 1) = C(3)(4) = 12C \Rightarrow C = \frac{1}{4}$$
8. **Decompose $$\frac{2s - 9}{(s - 1)(s - 5)}$$:**
$$\frac{2s - 9}{(s - 1)(s - 5)} = \frac{D}{s - 1} + \frac{E}{s - 5}$$
Multiply both sides:
$$2s - 9 = D(s - 5) + E(s - 1)$$
Plug in $$s=1$$:
$$2(1) - 9 = D(1 - 5) + E(0) \Rightarrow -7 = -4D \Rightarrow D = \frac{7}{4}$$
Plug in $$s=5$$:
$$2(5) - 9 = D(0) + E(5 - 1) \Rightarrow 1 = 4E \Rightarrow E = \frac{1}{4}$$
9. **Combine all partial fractions:**
$$Y(s) = -\frac{1}{s - 2} + \frac{3/4 + 7/4}{s - 1} + \frac{1/4 + 1/4}{s - 5} = -\frac{1}{s - 2} + \frac{10/4}{s - 1} + \frac{2/4}{s - 5}$$
Simplify coefficients:
$$Y(s) = -\frac{1}{s - 2} + \frac{5/2}{s - 1} + \frac{1/2}{s - 5}$$
10. **Take inverse Laplace transform:**
$$y(t) = -e^{2t} + \frac{5}{2}e^{t} + \frac{1}{2}e^{5t}$$
**Final answer:**
$$\boxed{y(t) = -e^{2t} + \frac{5}{2}e^{t} + \frac{1}{2}e^{5t}}$$
Laplace Ivp 4D2026
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