First_Equation 04049F
1. **State the problem:** Solve the first differential equation given: $$\frac{dy}{dx} + x^2 y^2 = x$$.
2. **Identify the type of equation:** This is a first-order nonlinear ordinary differential equation.
3. **Rewrite the equation:**
$$\frac{dy}{dx} = x - x^2 y^2$$
4. **Separate variables if possible:** Rewrite as
$$\frac{dy}{dx} = x - x^2 y^2 = x(1 - x y^2)$$
5. **Try substitution:** Let us try to separate variables by rewriting:
$$\frac{dy}{dx} = x - x^2 y^2$$
Rearranged:
$$\frac{dy}{dx} + x^2 y^2 = x$$
This is not separable in the usual way. Consider substitution or an integrating factor.
6. **Try substitution:** Let $v = y^2$, then $y = \sqrt{v}$ and
$$\frac{dy}{dx} = \frac{1}{2 \sqrt{v}} \frac{dv}{dx}$$
Substitute into the original equation:
$$\frac{1}{2 \sqrt{v}} \frac{dv}{dx} + x^2 v = x$$
Multiply both sides by $2 \sqrt{v}$:
$$\frac{dv}{dx} + 2 x^2 v \sqrt{v} = 2 x \sqrt{v}$$
7. **Rewrite:**
$$\frac{dv}{dx} = 2 x \sqrt{v} - 2 x^2 v \sqrt{v} = 2 x \sqrt{v} (1 - x v)$$
This is still complicated. Instead, try to solve the original equation by treating it as a Bernoulli equation.
8. **Bernoulli equation form:**
$$\frac{dy}{dx} + P(x) y = Q(x) y^n$$
Our equation is:
$$\frac{dy}{dx} + 0 \cdot y = x - x^2 y^2$$
Rewrite as:
$$\frac{dy}{dx} = x - x^2 y^2$$
Or:
$$\frac{dy}{dx} + x^2 y^2 = x$$
This is not in Bernoulli form directly. But if we write:
$$\frac{dy}{dx} = x - x^2 y^2$$
Try substitution $z = y^{-1}$, then $y = z^{-1}$ and
$$\frac{dy}{dx} = - z^{-2} \frac{dz}{dx}$$
Substitute into the equation:
$$- z^{-2} \frac{dz}{dx} = x - x^2 y^2 = x - x^2 z^{-2}$$
Multiply both sides by $- z^{2}$:
$$\frac{dz}{dx} = - x z^{2} + x^{2}$$
9. **Rewrite:**
$$\frac{dz}{dx} = x^{2} - x z^{2}$$
This is a nonlinear first-order ODE.
10. **Separate variables:**
$$\frac{dz}{dx} + x z^{2} = x^{2}$$
This is a Bernoulli equation with $n=2$, $P(x) = x$, $Q(x) = x^{2}$.
11. **Solve Bernoulli equation:**
Substitute $w = z^{1 - 2} = z^{-1}$, then
$$\frac{dw}{dx} = - z^{-2} \frac{dz}{dx}$$
From the equation:
$$\frac{dz}{dx} + x z^{2} = x^{2}$$
Multiply both sides by $- z^{-2}$:
$$- z^{-2} \frac{dz}{dx} - x = - x^{2} z^{-2}$$
But $- z^{-2} \frac{dz}{dx} = \frac{dw}{dx}$, so
$$\frac{dw}{dx} - x = - x^{2} w^{2}$$
This is complicated; however, since $w = z^{-1}$, the Bernoulli substitution should yield a linear ODE for $w$.
12. **Correct Bernoulli substitution:** For Bernoulli equation
$$\frac{dz}{dx} + P(x) z = Q(x) z^{n}$$
with $n=2$, substitute $w = z^{1 - n} = z^{-1}$, then
$$\frac{dw}{dx} = (1 - n) z^{-n} \frac{dz}{dx} = - z^{-2} \frac{dz}{dx}$$
Rewrite original equation:
$$\frac{dz}{dx} = x^{2} - x z^{2}$$
Multiply both sides by $- z^{-2}$:
$$- z^{-2} \frac{dz}{dx} = - z^{-2} x^{2} + x$$
But left side is $\frac{dw}{dx}$, so
$$\frac{dw}{dx} = - x^{2} w^{2} + x$$
This is nonlinear in $w$; however, the Bernoulli substitution should yield a linear ODE. The discrepancy suggests a misstep.
13. **Alternative approach:** Return to step 8 and try substitution $z = y^{-1}$:
Original equation:
$$\frac{dy}{dx} + x^{2} y^{2} = x$$
Substitute $y = \frac{1}{z}$, then
$$\frac{dy}{dx} = - \frac{1}{z^{2}} \frac{dz}{dx}$$
Substitute into the equation:
$$- \frac{1}{z^{2}} \frac{dz}{dx} + x^{2} \frac{1}{z^{2}} = x$$
Multiply both sides by $z^{2}$:
$$- \frac{dz}{dx} + x^{2} = x z^{2}$$
Rearranged:
$$\frac{dz}{dx} = x^{2} - x z^{2}$$
This matches step 9.
14. **Separate variables:**
$$\frac{dz}{dx} = x^{2} - x z^{2}$$
Rewrite as
$$\frac{dz}{dx} + x z^{2} = x^{2}$$
15. **Try substitution:** Let $u = z^{3}$, then
$$\frac{du}{dx} = 3 z^{2} \frac{dz}{dx}$$
From the equation:
$$\frac{dz}{dx} = x^{2} - x z^{2}$$
Multiply both sides by $3 z^{2}$:
$$3 z^{2} \frac{dz}{dx} = 3 z^{2} x^{2} - 3 x z^{4}$$
But $3 z^{2} \frac{dz}{dx} = \frac{du}{dx}$ and $z^{4} = z^{3} z = u z$, so
$$\frac{du}{dx} = 3 x^{2} z^{2} - 3 x u z$$
This is complicated; thus, try another method.
16. **Try to solve the equation numerically or by integrating factor:**
Rewrite:
$$\frac{dz}{dx} = x^{2} - x z^{2}$$
This is a Riccati equation.
17. **Summary:** The original equation is a Riccati equation and can be transformed into a second-order linear ODE by substitution.
18. **Final answer:** The solution requires advanced methods beyond this scope. The key step is substitution $z = y^{-1}$ leading to
$$\frac{dz}{dx} = x^{2} - x z^{2}$$
which is a Riccati equation.
**Slug:** first_equation
**Subject:** differential_equations