Chapter 11: Problem 42
For each of the following, graph the function, label the vertex, and draw the axis of symmetry. $$ f(x)=2(x+7)^{2} $$
Short Answer
Expert verified
Graph has a vertex at (-7,0) and axis of symmetry at x = -7.
Step by step solution
01
- Identify the Vertex
The function is in vertex form, which is given by: \text{\(f(x)=a(x-h)^{2}+k\)} Comparing it to \(f(x)=2(x+7)^{2}\), we find \(h=-7\) and \(k=0\). Therefore, the vertex of the function is at \((-7,0)\).
02
- Graph the Function
Plot the vertex \((-7,0)\) on the coordinate plane. The function \(f(x)=2(x+7)^{2}\) is a parabola that opens upwards (because the coefficient of \((x+7)^{2}\) is positive). For more accuracy, plot additional points by selecting values of \(x\) around -7 and calculating corresponding \(f(x)\) values (e.g., \(f(-8)\), \(f(-6)\)). Draw a smooth curve passing through these points and the vertex.
03
- Draw the Axis of Symmetry
The axis of symmetry for a parabola in vertex form \(f(x)=a(x-h)^{2}+k\) is the vertical line that passes through the vertex. For the function \(f(x)=2(x+7)^{2}\), the axis of symmetry is the line \(x=-7\). Draw a dashed vertical line at \(x=-7\) on the graph to represent the axis of symmetry.
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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 is a helpful format for graphing. It shows the vertex and opens the formula quickly. The general form for vertex form is given by:
\text{\(f(x)=a(x-h)^{2}+k\)}
Here, \text{\(h\)} and \text{\(k\)} are the coordinates of the vertex. The \text{\(a\)} represents the stretch factor. In our function \text{\(f(x)=2(x+7)^{2}\)}, comparing it with the general form, we see \text{\(h=-7\)} and \text{\(k=0\)}. Therefore, the vertex of this function is \text{\((-7,0)\)}. Knowing the vertex helps us position the parabola on the coordinate plane.
\text{\(f(x)=a(x-h)^{2}+k\)}
Here, \text{\(h\)} and \text{\(k\)} are the coordinates of the vertex. The \text{\(a\)} represents the stretch factor. In our function \text{\(f(x)=2(x+7)^{2}\)}, comparing it with the general form, we see \text{\(h=-7\)} and \text{\(k=0\)}. Therefore, the vertex of this function is \text{\((-7,0)\)}. Knowing the vertex helps us position the parabola on the coordinate plane.
parabola
A parabola is a U-shaped curve, and it’s the graph resulting from a quadratic function. The simplest parabola is \text{\(y=x^{2}\)}, which opens upwards. When a quadratic function is given in vertex form, \text{\(f(x)=a(x-h)^{2}+k\)}, it describes a parabola with vertex at \text{\((h,k)\)}.
- If \text{\(a\)} is positive, the parabola opens upwards.
- If \text{\(a\)} is negative, the parabola opens downwards.
axis of symmetry
The axis of symmetry is an imaginary line that divides the parabola into two mirror-image halves. For a quadratic function in vertex form \text{\(f(x)=a(x-h)^{2}+k\)}, the axis of symmetry is always the vertical line \text{\(x=h\)}.
In our example with \text{\(f(x)=2(x+7)^{2}\)}, since \text{\(h=-7\)}, the axis of symmetry is the vertical line \text{\(x=-7\)}. Drawing this line on the graph helps to visualize and confirm the symmetry of the parabola.
In our example with \text{\(f(x)=2(x+7)^{2}\)}, since \text{\(h=-7\)}, the axis of symmetry is the vertical line \text{\(x=-7\)}. Drawing this line on the graph helps to visualize and confirm the symmetry of the parabola.
vertex
The vertex of a parabola is its highest or lowest point, depending on its orientation. A quadratic function in vertex form easily reveals the vertex at \text{\((h,k)\)}. In our case, the function \text{\(f(x)=2(x+7)^{2}\)} has the vertex at \text{\((-7,0)\)}.
- The vertex is always a turning point for the graph.
- It represents the maximum or minimum value of the function, depending on whether the parabola opens downwards or upwards.
coordinate plane
The coordinate plane is a grid that helps to graph equations and functions. It consists of two axes: the horizontal (x-axis) and the vertical (y-axis). The point where they intersect is the origin \text{\((0,0)\)}. When graphing a quadratic function:
- Plot the vertex first on the coordinate plane.
- Use the axis of symmetry to guide additional point placement.
- Mark key points, plot them, and sketch the curve.