Chapter 8: Problem 4
Sketch the graph of each quadratic function. Label the vertex and sketch and label the axis of symmetry. See Examples I through 5 . $$ h(x)=x^{2}-4 $$
Short Answer
Expert verified
The vertex is at (0, -4), and the axis of symmetry is the line x = 0.
Step by step solution
01
Identify the Standard Form
The quadratic function given is \( h(x) = x^2 - 4 \). This is in the standard form of a quadratic function, \( y = ax^2 + bx + c \), where \( a = 1 \), \( b = 0 \), and \( c = -4 \).
02
Find the Vertex
For a quadratic function \( y = ax^2 + bx + c \), the vertex can be found using the formula \( x = -\frac{b}{2a} \). Substituting \( a = 1 \) and \( b = 0 \) gives \( x = -\frac{0}{2 \times 1} = 0 \). Substituting this value back into the function gives\( h(x) = (0)^2 - 4 = -4 \). Therefore, the vertex is at \( (0, -4) \).
03
Sketch the Axis of Symmetry
The axis of symmetry for the quadratic function \( y = ax^2 + bx + c \) is a vertical line through the x-coordinate of the vertex. Thus, the axis of symmetry is the line \( x = 0 \).
04
Identify Additional Points
To sketch the graph, identify additional points. Choose \( x = 1 \) and \( x = -1 \) as they are equidistant from the axis of symmetry. Substitute into \( h(x) = x^2 - 4 \):\( h(1) = 1^2 - 4 = -3 \) and \( h(-1) = (-1)^2 - 4 = -3 \). Thus, points are \( (1, -3) \) and \( (-1, -3) \).
05
Sketch the Graph
Plot the vertex \( (0, -4) \) and the additional points \( (1, -3) \) and \( (-1, -3) \). Draw a smooth U-shaped curve passing through these points. Label the vertex and the axis of symmetry. The graph opens upwards since \( a > 0 \).
06
Verify Symmetry
Ensure that the graph is symmetric about the vertical line \( x = 0 \) by checking points equidistant from \( x = 0 \), such as \( (1, -3) \) and \( (-1, -3) \).
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Vertex
In a quadratic function, the vertex is a crucial point that defines the graph's peak or trough. For the function \( h(x) = x^2 - 4 \), the vertex can be found using the formula \[ x = -\frac{b}{2a} \]
- Here, \( a = 1 \) and \( b = 0 \), so \( x = 0 \).
- Substitute \( x = 0 \) into the function to find the y-coordinate: \( h(x) = (0)^2 - 4 = -4 \).
Axis of Symmetry
The axis of symmetry in a quadratic function is a vertical line that passes through the vertex. It divides the parabola into two mirror-image halves. For the function \( h(x) = x^2 - 4 \), the axis of symmetry is determined by the x-coordinate of the vertex.
- Since the vertex is at \( (0, -4) \), the axis of symmetry is the line \( x = 0 \).
Graph Sketching
Graph sketching involves creating a visual representation of a quadratic function, making it easier to interpret. To sketch \( h(x) = x^2 - 4 \):
- Start by plotting the vertex \( (0, -4) \).
- The axis of symmetry, \( x = 0 \), divides the graph into two equal parts.
- Pick additional points such as \( (1, -3) \) and \( (-1, -3) \), which are equidistant from the axis of symmetry.