Chapter 11: Problem 37
Graph each parabola. Give the vertex, axis of symmetry, domain, and range. $$ x=-\frac{1}{5} y^{2}+2 y-4 $$
Short Answer
Expert verified
Vertex: (2, -4), Axis of symmetry: \( x = 2 \, Domain: \( (-\text{∞}, \text{∞}) \), Range: \( [-4, \text{∞}) \)
Step by step solution
01
- Identify the vertex form
Identify the function's form. The given function is in the vertex form:\[ f(x) = a(x-h)^2 + k \]where \(a = 2, h = 2, k = -4\)
02
- Determine the vertex
From the vertex form, the vertex \( (h, k) \) can be extracted:Vertex: (2, -4)
03
- Find the axis of symmetry
The axis of symmetry is a vertical line that passes through the vertex. It has the equation \( x = h \):Axis of symmetry: \( x = 2 \)
04
- Identify the domain
The domain of a parabola that is a quadratic function such as this one is all real numbers:Domain: \( (-\text{∞}, \text{∞}) \)
05
- Determine the range
Since \( a = 2 \) is positive, the parabola opens upwards. The range starts from the vertex's y-value and goes to \text{∞}:Range: \( [-4, \text{∞}) \)
06
- Plotting the graph
To graph the parabola:1. Plot the vertex at (2, -4).2. Draw the axis of symmetry, \( x = 2 \).3. Use additional points on either side of the axis of symmetry to get the shape, e.g., \( x = 1 \) and \( x = 3 \).4. Sketch the parabola, ensuring it opens upwards.
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
vertex form
The vertex form of a quadratic function makes it very easy to identify the graph's vertex. This form is given by ewline f(x) = a(x-h)^2 + k.ewline Here,
- a represents the vertical stretch or compression.
- h is the x-coordinate of the vertex.
- k is the y-coordinate of the vertex.
axis of symmetry
The axis of symmetry is a line that divides the parabola into two mirror images. For a quadratic function in vertex form f(x) = a(x-h)^2 + k, the axis of symmetry is always x = h.ewline For our function f(x) = 2(x-2)^2 -4, the axis of symmetry is x = 2. This vertical line passes through the vertex and ensures the parabola looks the same on both sides of this line.
domain and range
Understanding the domain and range of a quadratic function helps describe all possible values of x (domain) and f(x) (range).ewline Domain:
Range:
- For any quadratic function, the domain is always all real numbers since we can plug any x-value into the function and compute an output.
- Therefore, the domain of f(x) = 2(x-2)^2 - 4 is (-∞, ∞).
Range:
- The range relates to the output values, or f(x).
- Since the parabola opens upwards (because a > 0), the minimum point of the parabola is the vertex. Thus, the range starts from the y-coordinate of the vertex and goes to positive infinity.
- Therefore, the range of f(x) = 2(x-2)^2 - 4 is [-4, ∞).
quadratic functions
Quadratic functions form the core of parabolas in algebra. A quadratic function typically looks like f(x) = ax^2 + bx + c, where a, b, and c are constants.
- If the coefficient 'a' is positive, the parabola opens upwards. If 'a' is negative, it opens downwards.
- The vertex formula for converting to vertex form provides an efficient way to graph these functions. Our example function, f(x) = 2(x-2)^2 -4, is already in vertex form.
- To graph, find the vertex, plot it, draw the axis of symmetry, add additional points around the vertex, and sketch the curve.