1. **State the problem:** Solve the differential equation $$\frac{dy}{dp} = B(6400y - y^2)$$ where $B$ is a constant.
2. **Rewrite the equation:** Factor the right side:
$$\frac{dy}{dp} = B y (6400 - y)$$
3. **Separate variables:**
$$\frac{dy}{y(6400 - y)} = B \, dp$$
4. **Partial fraction decomposition:**
Express $$\frac{1}{y(6400 - y)}$$ as $$\frac{A}{y} + \frac{C}{6400 - y}$$.
Multiply both sides by $$y(6400 - y)$$:
$$1 = A(6400 - y) + C y = 6400 A - A y + C y$$
Group terms:
$$1 = 6400 A + y(C - A)$$
Equate coefficients:
- Constant term: $$6400 A = 1 \implies A = \frac{1}{6400}$$
- Coefficient of $$y$$: $$C - A = 0 \implies C = A = \frac{1}{6400}$$
5. **Rewrite integral:**
$$\int \frac{dy}{y(6400 - y)} = \int \left( \frac{1}{6400 y} + \frac{1}{6400 (6400 - y)} \right) dy$$
6. **Integrate both sides:**
$$\int \left( \frac{1}{6400 y} + \frac{1}{6400 (6400 - y)} \right) dy = \int B \, dp$$
Calculate each integral:
- $$\int \frac{1}{6400 y} dy = \frac{1}{6400} \ln|y|$$
- $$\int \frac{1}{6400 (6400 - y)} dy = -\frac{1}{6400} \ln|6400 - y|$$ (because derivative of denominator is $$-1$$)
So,
$$\frac{1}{6400} \ln|y| - \frac{1}{6400} \ln|6400 - y| = B p + C$$
7. **Combine logarithms:**
$$\frac{1}{6400} \ln \left| \frac{y}{6400 - y} \right| = B p + C$$
Multiply both sides by 6400:
$$\ln \left| \frac{y}{6400 - y} \right| = 6400 B p + 6400 C$$
Let $$C_1 = 6400 C$$ (a constant), then
$$\ln \left| \frac{y}{6400 - y} \right| = 6400 B p + C_1$$
8. **Exponentiate both sides:**
$$\left| \frac{y}{6400 - y} \right| = e^{6400 B p + C_1} = C_2 e^{6400 B p}$$ where $$C_2 = e^{C_1} > 0$$
9. **Solve for $$y$$:**
Assuming positive values,
$$\frac{y}{6400 - y} = C_2 e^{6400 B p}$$
Multiply both sides by $$6400 - y$$:
$$y = C_2 e^{6400 B p} (6400 - y) = 6400 C_2 e^{6400 B p} - C_2 e^{6400 B p} y$$
Bring terms with $$y$$ to one side:
$$y + C_2 e^{6400 B p} y = 6400 C_2 e^{6400 B p}$$
Factor $$y$$:
$$y (1 + C_2 e^{6400 B p}) = 6400 C_2 e^{6400 B p}$$
Divide both sides:
$$y = \frac{6400 C_2 e^{6400 B p}}{1 + C_2 e^{6400 B p}}$$
10. **Final solution:**
$$\boxed{y(p) = \frac{6400 C e^{6400 B p}}{1 + C e^{6400 B p}}}$$ where $$C$$ is an arbitrary constant determined by initial conditions.
This is the general solution to the given differential equation.
Logistic Differential 082Bdc
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