Chapter 12: Problem 26
For quadratic function, identify the vertex, axis of symmetry, and \(x\)- and \(y\)-intercepts. Then, graph the function. \(f(x)=2(x-3)^{2}+3\)
Short Answer
Expert verified
Vertex: (3, 3)
Axis of symmetry: x = 3
x-intercepts: None
y-intercept: (0, 21)
To graph the function, plot the vertex (3, 3), the y-intercept (0, 21), the axis of symmetry at x=3, and connect the points to form a parabola with symmetry around the axis of symmetry.
Step by step solution
01
Identify Vertex #
The given quadratic function is \(f(x) = 2(x-3)^2 +3\). Since the function is in vertex form \((f(x)=a(x-h)^2+k)\), we can directly read the vertex's coordinates \((h,k)\) from the equation.
In our case, the vertex is point (3, 3).
02
Find Axis of Symmetry #
The axis of symmetry of a parabola always passes through the vertex, and for a vertical parabola, it is a vertical line. The equation for the axis of symmetry in such cases will be x=h, with h being the x-coordinate of the vertex.
Here, the axis of symmetry is x=3.
03
Find x-intercepts #
To find the x-intercepts of the given function, we need to find the x-values when f(x) = 0:
\(0 = 2(x-3)^2 + 3\)
Now we solve for x:
\(-3 = 2(x-3)^2\)
\(\frac{-3}{2} = (x-3)^2\)
Since the expression on the right-hand side of the equation is a squared term, it must be non-negative. However, the left-hand side is negative (-3/2), which means there are no x-intercepts in this particular function.
04
Find y-intercepts #
To find the y-intercepts of the given function, we need to find the f(x) value when x = 0:
\(f(0) = 2 (0-3)^2 + 3\)
\(f(0) = 2(9) + 3\)
\(f(0) = 18 + 3\)
\(f(0) = 21\)
So, the y-intercept of the function is the point (0, 21).
05
Graph the Function #
To graph the function, follow these steps:
1. Draw the axis of symmetry (x=3).
2. Plot the vertex at point (3, 3).
3. Plot the y-intercept at point (0, 21).
4. Since we know that the function is symmetric with respect to the axis of symmetry (x=3), plot additional points by reflecting the y-intercept with respect to the axis of symmetry.
5. Draw the parabola by connecting the points plotted above, maintaining symmetry around the axis of symmetry (x=3).
Now you have successfully graphed the given quadratic function: \(f(x)=2(x-3)^{2}+3\).
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Vertex Form
Quadratic functions can be expressed in a special format known as vertex form. This form is useful for quickly identifying certain characteristics of the parabola. The general equation is
- \(f(x) = a(x-h)^2 + k\)
- \(a\) controls the parabola's width and direction – wider, narrower, opening upwards or downwards.
- \(h\) and \(k\) determine the coordinates of the vertex \((h, k)\).
Axis of Symmetry
The axis of symmetry is a vital part of understanding and graphing quadratic functions. This is a vertical line that divides the parabola into two mirror images. For parabolas in vertex form, the axis of symmetry can be quickly identified as:
It helps ensure that any point on the parabola on one side of the axis has a corresponding point on the other side, making graph plotting simpler and more accurate.
- \(x = h\)
It helps ensure that any point on the parabola on one side of the axis has a corresponding point on the other side, making graph plotting simpler and more accurate.
Graphing Parabolas
Graphing a parabola involves several steps, starting from identifying key features of the quadratic equation:
- Determine the vertex from the vertex form, as it gives a starting reference point.
- Locate the axis of symmetry which helps in ensuring the shape of the graph is accurate.
- Identify the intercepts to mark more specific points on the graph.
- Draw a smooth symmetric curve through these points, extending it as needed.
- Vertex at (3, 3).
- Axis of symmetry at \(x = 3\).
- Add points such as y-intercept at (0, 21).
X-Intercepts
The x-intercepts of a quadratic function are points where the graph crosses the x-axis. This means that the function’s value is zero at these points, or:
- \(f(x) = 0\)
- \(f(x) = 2(x-3)^2 + 3\)
- \(0 = 2(x-3)^2 + 3\)
- \((x-3)^2 = -\frac{3}{2}\)
- there are no x-intercepts.
Y-Intercepts
The y-intercepts are the points where the graph crosses the y-axis. This occurs when the x-value is zero. Finding the y-intercept involves substituting zero for x in the function:
- \(f(0) = 2(0-3)^2 + 3\)
- \(f(0) = 2 \cdot 9 + 3 = 21\)
- at the point (0, 21).