Hyperbola Equations
1. **Problem 1: Find the general equation of the hyperbola with vertices (0, ±2) and foci (0, ±2\sqrt{5})**.
Step 1: Identify the orientation and parameters.
- The vertices are on the y-axis at (0, ±2), so the hyperbola is vertical.
- Center is at the origin (0,0).
- Distance from center to vertex: $a=2$.
- Distance from center to foci: $c=2\sqrt{5}$.
Step 2: Use relationship between $a$, $b$, and $c$ for hyperbolas:
$$ c^2 = a^2 + b^2 $$
Substitute values:
$$ (2\sqrt{5})^2 = 2^2 + b^2 $$
$$ 4 \times 5 = 4 + b^2 $$
$$ 20 = 4 + b^2 $$
$$ b^2 = 16 $$
Step 3: Write the standard form equation for vertical hyperbola centered at origin:
$$ \frac{y^2}{a^2} - \frac{x^2}{b^2} = 1 $$
Substitute values:
$$ \frac{y^2}{4} - \frac{x^2}{16} = 1 $$
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2. **Problem 2: Find an equation of the hyperbola in standard form having a focus at (5, 0) and ends of its conjugate axis at (0, ±2)**.
Step 1: Analyze given points.
- Focus at (5,0) means hyperbola is horizontal and center is on x-axis.
- Ends of conjugate axis at (0, ±2) means center y=0 and conjugate axis length is vertical.
Step 2: The conjugate axis length is $2b=4$, so $b=2$.
- Since conjugate axis endpoints are at (0, ±2), center at (0,0).
Step 3: The focus is at (5,0), so $c=5$ (distance from center).
Step 4: Use relationship:
$$ c^2 = a^2 + b^2 $$
$$ 5^2 = a^2 + 2^2 $$
$$ 25 = a^2 + 4 $$
$$ a^2 = 21 $$
Step 5: Write the standard form for horizontal hyperbola centered at origin:
$$ \frac{x^2}{a^2} - \frac{y^2}{b^2} = 1 $$
Substitute:
$$ \frac{x^2}{21} - \frac{y^2}{4} = 1 $$
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**Final answers:**
1) $$ \frac{y^2}{4} - \frac{x^2}{16} = 1 $$
2) $$ \frac{x^2}{21} - \frac{y^2}{4} = 1 $$