Implicit Tangents 10Eb6C
1. **Problem statement:** Find the equation(s) of the tangent(s) to the curve $$x^2 y^2 + y^2 + x^3 = 5$$ at points where $$x=1$$ using implicit differentiation.
2. **Formula and rules:** To find the slope of the tangent line, we differentiate both sides of the equation implicitly with respect to $$x$$, treating $$y$$ as a function of $$x$$ (i.e., $$y = y(x)$$). Use the product rule and chain rule:
$$\frac{d}{dx}[x^2 y^2] + \frac{d}{dx}[y^2] + \frac{d}{dx}[x^3] = \frac{d}{dx}[5]$$
3. **Differentiate each term:**
- For $$x^2 y^2$$, use product rule:
$$\frac{d}{dx}[x^2 y^2] = 2x y^2 + x^2 \cdot 2y \frac{dy}{dx} = 2x y^2 + 2x^2 y \frac{dy}{dx}$$
- For $$y^2$$, use chain rule:
$$\frac{d}{dx}[y^2] = 2y \frac{dy}{dx}$$
- For $$x^3$$:
$$\frac{d}{dx}[x^3] = 3x^2$$
- Right side derivative is zero:
$$\frac{d}{dx}[5] = 0$$
4. **Combine derivatives:**
$$2x y^2 + 2x^2 y \frac{dy}{dx} + 2y \frac{dy}{dx} + 3x^2 = 0$$
5. **Group terms with $$\frac{dy}{dx}$$:**
$$2x^2 y \frac{dy}{dx} + 2y \frac{dy}{dx} = -2x y^2 - 3x^2$$
6. **Factor out $$\frac{dy}{dx}$$:**
$$\frac{dy}{dx} (2x^2 y + 2y) = -2x y^2 - 3x^2$$
7. **Solve for $$\frac{dy}{dx}$$:**
$$\frac{dy}{dx} = \frac{-2x y^2 - 3x^2}{2y (x^2 + 1)}$$
8. **Find $$y$$ values at $$x=1$$:** Substitute $$x=1$$ into original equation:
$$1^2 y^2 + y^2 + 1^3 = 5 \implies y^2 + y^2 + 1 = 5 \implies 2y^2 = 4 \implies y^2 = 2 \implies y = \pm \sqrt{2}$$
9. **Calculate slopes at points:**
- At $$(1, \sqrt{2})$$:
$$\frac{dy}{dx} = \frac{-2(1)(2) - 3(1)^2}{2(\sqrt{2})(1 + 1)} = \frac{-4 - 3}{2 \sqrt{2} \cdot 2} = \frac{-7}{4 \sqrt{2}} = -\frac{7 \sqrt{2}}{8}$$
- At $$(1, -\sqrt{2})$$:
$$\frac{dy}{dx} = \frac{-4 - 3}{2(-\sqrt{2})(2)} = \frac{-7}{-4 \sqrt{2}} = \frac{7 \sqrt{2}}{8}$$
10. **Write tangent line equations:**
Use point-slope form $$y - y_1 = m(x - x_1)$$:
- For $$(1, \sqrt{2})$$:
$$y - \sqrt{2} = -\frac{7 \sqrt{2}}{8} (x - 1)$$
- For $$(1, -\sqrt{2})$$:
$$y + \sqrt{2} = \frac{7 \sqrt{2}}{8} (x - 1)$$
**Final answer:**
$$\boxed{\begin{cases} y - \sqrt{2} = -\frac{7 \sqrt{2}}{8} (x - 1) \\ y + \sqrt{2} = \frac{7 \sqrt{2}}{8} (x - 1) \end{cases}}$$