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. **Identify the type:** This is a Riccati equation of the form $$y' = a(x) y^2 + b(x) y + c(x)$$ with $$a(x) = \frac{1}{x}, b(x) = \frac{1}{x}, c(x) = -\frac{2}{x}$$.
3. **Use the known solution:** Since $$y_1 = 1$$ is a particular solution, substitute $$y = y_1 + \frac{1}{u} = 1 + \frac{1}{u}$$ to transform the Riccati equation into a linear equation in $$u$$.
4. **Compute $$y'$$:**
$$y' = \frac{d}{dx} \left(1 + \frac{1}{u} \right) = -\frac{u'}{u^2}$$.
5. **Substitute into the original equation:**
$$-\frac{u'}{u^2} = \frac{1}{x} \left(1 + \frac{1}{u} \right)^2 + \frac{1}{x} \left(1 + \frac{1}{u} \right) - \frac{2}{x}$$.
6. **Expand the right side:**
$$\left(1 + \frac{1}{u} \right)^2 = 1 + \frac{2}{u} + \frac{1}{u^2}$$
So,
$$\frac{1}{x} \left(1 + \frac{2}{u} + \frac{1}{u^2} \right) + \frac{1}{x} \left(1 + \frac{1}{u} \right) - \frac{2}{x} = \frac{1}{x} + \frac{2}{x u} + \frac{1}{x u^2} + \frac{1}{x} + \frac{1}{x u} - \frac{2}{x}$$
7. **Simplify the right side:**
$$\frac{1}{x} + \frac{1}{x} - \frac{2}{x} = 0$$
and
$$\frac{2}{x u} + \frac{1}{x u} = \frac{3}{x u}$$
So the right side is
$$\frac{1}{x u^2} + \frac{3}{x u}$$.
8. **Rewrite the equation:**
$$-\frac{u'}{u^2} = \frac{1}{x u^2} + \frac{3}{x u}$$
Multiply both sides by $$u^2$$:
$$-u' = \frac{1}{x} + \frac{3 u}{x}$$
9. **Rearranged:**
$$u' + \frac{3}{x} u = -\frac{1}{x}$$
10. **Solve the linear ODE for $$u$$:**
The integrating factor is
$$\mu(x) = e^{\int \frac{3}{x} dx} = e^{3 \ln |x|} = x^3$$.
11. **Multiply both sides by $$x^3$$:**
$$x^3 u' + 3 x^2 u = -x^2$$
which is
$$(x^3 u)' = -x^2$$.
12. **Integrate both sides:**
$$x^3 u = -\int x^2 dx + C = -\frac{x^3}{3} + C$$
13. **Solve for $$u$$:**
$$u = -\frac{x^3}{3 x^3} + \frac{C}{x^3} = -\frac{1}{3} + \frac{C}{x^3}$$
14. **Recall substitution:**
$$y = 1 + \frac{1}{u} = 1 + \frac{1}{-\frac{1}{3} + \frac{C}{x^3}} = 1 + \frac{1}{\frac{C}{x^3} - \frac{1}{3}}$$
15. **Simplify denominator:**
$$\frac{C}{x^3} - \frac{1}{3} = \frac{3 C - x^3}{3 x^3}$$
16. **Final solution:**
$$y = 1 + \frac{1}{\frac{3 C - x^3}{3 x^3}} = 1 + \frac{3 x^3}{3 C - x^3} = \frac{3 C - x^3 + 3 x^3}{3 C - x^3} = \frac{3 C + 2 x^3}{3 C - x^3}$$
**Answer:**
$$\boxed{y = \frac{3 C + 2 x^3}{3 C - x^3}}$$ where $$C$$ is an arbitrary constant.
Riccati Equation 4Aaf70
Step-by-step solutions with LaTeX - clean, fast, and student-friendly.