Chapter 11: Problem 48
Find the vertex, focus, and directrix of each parabola. Graph the equation. \((x-2)^{2}=4(y-3)\)
Short Answer
Expert verified
Vertex: (2, 3), Focus: (2, 4), Directrix: y = 2
Step by step solution
01
- Identify the Standard Form
The given equation \((x-2)^{2}=4(y-3)\) is in the standard form of a parabola \((x-h)^2 = 4p(y-k)\).
02
- Identify the Vertex
From the standard form, the vertex (\(h, k)\) can be determined directly. Here, \(h = 2\) and \(k = 3\). Therefore, the vertex of the parabola is at \( (2, 3) \).
03
- Determine the Value of p
By comparing \( 4p \) with the coefficient in the equation, \(4 = 4p\), solve for \(p\). Thus, \(p = 1\).
04
- Find the Focus
The focus of a parabola \((x-h)^2 = 4p(y-k)\) is \((h, k + p)\). Substituting the values, we get the focus \( (2, 3+1) = (2, 4) \).
05
- Find the Directrix
The directrix of a parabola \((x-h)^2 = 4p(y-k)\) is given by the line \( y = k - p \). Plugging in the values, we get the directrix: \( y = 3 - 1 = 2 \).
06
- Graph the Parabola
To graph the parabola, plot the vertex \( (2, 3) \), the focus \((2, 4) \), and the directrix \(( y = 2 )\). Sketch the parabola opening upwards with these points in mind.
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Understanding the Parabola Standard Form
The standard form of a parabola is a simplified way to understand its equation and key features. For a parabola that opens upwards or downwards, the standard form is \((x-h)^2 = 4p(y-k)\). Here:
- \(h\) and \(k\): the coordinates of the vertex
- \(p\): the distance from the vertex to the focus, which also determines how 'wide' or 'narrow' the parabola is
Vertex Calculation
Finding the vertex of a parabola is straightforward when it's in standard form. The vertex \((h, k)\) represents the point where the parabola changes direction. From the equation \((x-2)^{2}=4(y-3)\), we can identify \h\ and \k\ directly:
- \h = 2\
- \k = 3\
Focus Calculation
The focus of a parabola is a point that helps define its shape. In the standard form \((x-h)^2 = 4p(y-k)\), the focus lies at \((h, k + p)\).To find the focus, first determine \p\. In our case, equate \4p\ with the coefficient of the equation:
- \4p = 4\
- \p = 1\
- \h = 2\
- \k = 3\
- \p = 1\
Directrix Calculation
The directrix of a parabola is a line that is perpendicular to its axis of symmetry. In the standard form \((x-h)^2 = 4p(y-k)\), the directrix is given by \y = k - p\.Here’s how to find it:
- Identify \k\: \k = 3\
- Identify \p\: \p = 1\