1. **State the problem:** We are given the line equation $y = 4x - 1$ and the conic equation $x^2 + 2x + y^2 = k$. We want to analyze the relationship between these two equations.
2. **Substitute $y$ from the line into the conic:** Replace $y$ in the conic equation with $4x - 1$:
$$x^2 + 2x + (4x - 1)^2 = k$$
3. **Expand the squared term:**
$$(4x - 1)^2 = 16x^2 - 8x + 1$$
4. **Rewrite the conic equation:**
$$x^2 + 2x + 16x^2 - 8x + 1 = k$$
5. **Combine like terms:**
$$17x^2 - 6x + 1 = k$$
6. **Rearrange to standard quadratic form:**
$$17x^2 - 6x + (1 - k) = 0$$
7. **Interpretation:** This quadratic in $x$ represents the intersection points of the line and the conic for a given $k$. The number of real solutions depends on the discriminant:
$$\Delta = (-6)^2 - 4 \cdot 17 \cdot (1 - k) = 36 - 68 + 68k = 68k - 32$$
8. **Condition for intersection:**
- If $\Delta > 0$, two distinct intersection points.
- If $\Delta = 0$, one tangent point.
- If $\Delta < 0$, no real intersection.
9. **Solve for $k$ to find intersection conditions:**
$$68k - 32 \geq 0 \implies k \geq \frac{32}{68} = \frac{8}{17}$$
**Final answer:** The line $y=4x-1$ intersects the conic $x^2 + 2x + y^2 = k$ if and only if $k \geq \frac{8}{17}$.
Line Conic Intersection
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