1. **State the problem:** Solve the differential equation
$$y - x \left(\frac{dy}{dx}\right) = a \left(y^2 + \frac{dy}{dx}\right).$$
2. **Rewrite the equation:** Group terms involving $\frac{dy}{dx}$ on one side:
$$y - x \frac{dy}{dx} = a y^2 + a \frac{dy}{dx}$$
Move all $\frac{dy}{dx}$ terms to the left and others to the right:
$$- x \frac{dy}{dx} - a \frac{dy}{dx} = a y^2 - y$$
3. **Factor out $\frac{dy}{dx}$ on the left:**
$$\left(-x - a\right) \frac{dy}{dx} = a y^2 - y$$
4. **Isolate $\frac{dy}{dx}$:**
$$\frac{dy}{dx} = \frac{a y^2 - y}{-x - a} = \frac{a y^2 - y}{-(x + a)} = -\frac{a y^2 - y}{x + a}$$
5. **Rewrite as:**
$$\frac{dy}{dx} = -\frac{a y^2 - y}{x + a}$$
6. **Separate variables:**
$$\frac{dy}{a y^2 - y} = -\frac{dx}{x + a}$$
7. **Factor denominator in $y$ integral:**
$$a y^2 - y = y (a y - 1)$$
So,
$$\frac{dy}{y (a y - 1)} = -\frac{dx}{x + a}$$
8. **Use partial fractions for the left side:**
Assume
$$\frac{1}{y (a y - 1)} = \frac{A}{y} + \frac{B}{a y - 1}$$
Multiply both sides by $y (a y - 1)$:
$$1 = A (a y - 1) + B y = A a y - A + B y = y (A a + B) - A$$
Equate coefficients:
- Constant term: $-A = 1 \Rightarrow A = -1$
- Coefficient of $y$: $A a + B = 0 \Rightarrow -1 \cdot a + B = 0 \Rightarrow B = a$
9. **Rewrite integral:**
$$\int \frac{dy}{y (a y - 1)} = \int \left(-\frac{1}{y} + \frac{a}{a y - 1}\right) dy = \int -\frac{1}{y} dy + \int \frac{a}{a y - 1} dy$$
10. **Integrate each term:**
- $$\int -\frac{1}{y} dy = -\ln|y|$$
- For $$\int \frac{a}{a y - 1} dy$$, substitute $u = a y - 1$, so $du = a dy$, $dy = \frac{du}{a}$:
$$\int \frac{a}{u} \cdot \frac{du}{a} = \int \frac{1}{u} du = \ln|u| = \ln|a y - 1|$$
11. **Combine integrals:**
$$\int \frac{dy}{y (a y - 1)} = -\ln|y| + \ln|a y - 1| + C_1 = \ln \left|\frac{a y - 1}{y}\right| + C_1$$
12. **Integrate right side:**
$$\int -\frac{dx}{x + a} = -\ln|x + a| + C_2$$
13. **Set integrals equal:**
$$\ln \left|\frac{a y - 1}{y}\right| + C_1 = -\ln|x + a| + C_2$$
Combine constants $C = C_2 - C_1$:
$$\ln \left|\frac{a y - 1}{y}\right| = -\ln|x + a| + C$$
14. **Exponentiate both sides:**
$$\left|\frac{a y - 1}{y}\right| = e^{C} \cdot \frac{1}{|x + a|}$$
Let $K = e^{C} > 0$:
$$\left|\frac{a y - 1}{y}\right| = \frac{K}{|x + a|}$$
15. **Write general implicit solution:**
$$\frac{a y - 1}{y} = \pm \frac{K}{x + a}$$
Or equivalently,
$$\frac{a y - 1}{y} (x + a) = \pm K$$
This is the implicit solution to the differential equation.
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**Final answer:**
$$\frac{a y - 1}{y} (x + a) = C,$$
where $C$ is an arbitrary constant.
Diff Eq Solution 22D473
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