1. **State the problem:** Solve the differential equation $$y' = \frac{1}{x}y^2 + \frac{1}{x}y - \frac{2}{x}$$ given that $$y=1$$ is a solution.
2. **Rewrite the equation:** Factor out $$\frac{1}{x}$$:
$$y' = \frac{1}{x}(y^2 + y - 2)$$
3. **Check the given solution:** Substitute $$y=1$$:
$$y' = \frac{1}{x}(1 + 1 - 2) = \frac{0}{x} = 0$$
This confirms $$y=1$$ is a constant solution.
4. **Use substitution to reduce order:** Let $$y = 1 + \frac{1}{v}$$, so that we transform the equation to solve for $$v$$.
5. **Find $$y'$$ in terms of $$v$$:**
$$y' = -\frac{1}{v^2}v'$$
6. **Substitute into the original equation:**
$$-\frac{1}{v^2}v' = \frac{1}{x} \left( \left(1 + \frac{1}{v}\right)^2 + \left(1 + \frac{1}{v}\right) - 2 \right)$$
7. **Simplify the right side:**
$$\left(1 + \frac{1}{v}\right)^2 + \left(1 + \frac{1}{v}\right) - 2 = 1 + \frac{2}{v} + \frac{1}{v^2} + 1 + \frac{1}{v} - 2 = \frac{3}{v} + \frac{1}{v^2}$$
8. **Rewrite the equation:**
$$-\frac{1}{v^2}v' = \frac{1}{x} \left( \frac{3}{v} + \frac{1}{v^2} \right)$$
9. **Multiply both sides by $$v^2$$:**
$$-v' = \frac{1}{x}(3v + 1)$$
10. **Rewrite as:**
$$v' + \frac{3}{x}v = -\frac{1}{x}$$
11. **This is a linear first-order ODE in $$v$$.** The integrating factor is:
$$\mu(x) = e^{\int \frac{3}{x} dx} = e^{3 \ln |x|} = |x|^3$$
12. **Multiply both sides by $$\mu(x)$$:**
$$x^3 v' + 3x^2 v = -x^2$$
13. **Left side is derivative:**
$$\frac{d}{dx}(x^3 v) = -x^2$$
14. **Integrate both sides:**
$$x^3 v = -\int x^2 dx + C = -\frac{x^3}{3} + C$$
15. **Solve for $$v$$:**
$$v = \frac{C}{x^3} - \frac{1}{3}$$
16. **Recall substitution:**
$$y = 1 + \frac{1}{v} = 1 + \frac{1}{\frac{C}{x^3} - \frac{1}{3}} = 1 + \frac{1}{\frac{C - \frac{x^3}{3}}{x^3}} = 1 + \frac{x^3}{C - \frac{x^3}{3}}$$
17. **Simplify denominator:**
$$C - \frac{x^3}{3} = \frac{3C - x^3}{3}$$
18. **Final solution:**
$$y = 1 + \frac{x^3}{\frac{3C - x^3}{3}} = 1 + \frac{3x^3}{3C - x^3}$$
19. **Rewrite neatly:**
$$\boxed{y = 1 + \frac{3x^3}{3C - x^3}}$$
This is the general solution to the differential equation given the particular solution $$y=1$$.
Solve Differential 003E2D
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