Linear Differential 25998B
1. **Problem Statement:** Solve the differential equation $$\frac{dy}{dt} = -\frac{y}{t} + 2$$ for the general solution.
2. **Identify the type of equation:** This is a first-order linear differential equation of the form $$\frac{dy}{dt} + P(t)y = Q(t)$$ where $$P(t) = \frac{1}{t}$$ (note the sign change when rearranged) and $$Q(t) = 2$$.
3. **Rewrite the equation:** Move all terms to standard form:
$$\frac{dy}{dt} + \frac{1}{t}y = 2$$
4. **Find the integrating factor (IF):** The integrating factor is given by
$$\mu(t) = e^{\int P(t) dt} = e^{\int \frac{1}{t} dt} = e^{\ln|t|} = |t|$$
Assuming $$t > 0$$ for simplicity, $$\mu(t) = t$$.
5. **Multiply the entire differential equation by the integrating factor:**
$$t \frac{dy}{dt} + t \cdot \frac{1}{t} y = 2t$$
which simplifies to
$$t \frac{dy}{dt} + y = 2t$$
6. **Recognize the left side as a derivative:**
$$\frac{d}{dt}(ty) = 2t$$
7. **Integrate both sides with respect to $$t$$:**
$$\int \frac{d}{dt}(ty) dt = \int 2t dt$$
$$ty = t^2 + C$$
8. **Solve for $$y$$:**
$$y = \frac{t^2 + C}{t} = t + \frac{C}{t}$$
**Final answer:**
$$\boxed{y = t + \frac{C}{t}}$$
This solution shows how to use an integrating factor to solve a linear first-order differential equation by converting it into an exact derivative, integrating, and then solving for the dependent variable.