Chapter 8: Problem 36
Graph the function and find the vertex, the axis of symmetry, and the maximum value or the minimum value. $$ f(x)=(x+3)^{2}-2 $$
Short Answer
Expert verified
Vertex: (-3, -2). Axis of symmetry: x = -3. Minimum value: -2. The parabola opens upwards.
Step by step solution
01
Identify the function's form
The given function is \[ f(x) = (x+3)^2 -2 \] which is a quadratic function in the form \[ f(x) = a(x-h)^2 + k \] where \( a = 1 \), \( h = -3 \), and \( k = -2 \).
02
Find the vertex
The vertex \((h, k)\) is given by the values of \( h \) and \( k \) in the vertex form. Therefore, the vertex is \[ (-3, -2) \].
03
Determine the axis of symmetry
The axis of symmetry for a parabola in the form \[ f(x) = a(x-h)^2 + k \] is the vertical line \( x = h \). Therefore, for the given function, the axis of symmetry is \[ x = -3 \].
04
Identify the direction of the parabola
Since the coefficient \( a = 1 \) is positive, the parabola opens upwards. This means the function has a minimum value.
05
Find the minimum value
The minimum value of the function \[ f(x) = a(x-h)^2 + k \] occurs at the vertex. Therefore, the minimum value is \[ f(-3) = -2 \].
06
Graph the function
To graph the function, plot the vertex \((-3, -2)\). Then draw the parabola opening upwards, making sure it is symmetrical around the axis of symmetry \( x = -3 \).
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Vertex Form of a Parabola
The vertex form of a quadratic function is a key concept in graphing and analyzing parabolas. It is written as follows: \text { f(x) = a(x-h)^2 + k } Here,
- \(a\): Determines the width and direction (upward if positive, downward if negative) of the parabola.
- \(h\): The \(x\)-coordinate of the vertex.
- \(k\): The \(y\)-coordinate of the vertex.
Axis of Symmetry
The axis of symmetry in a quadratic function is a vertical line that passes through the vertex. This line divides the parabola into two mirrored halves. For the vertex form \text{ f(x) = a(x-h)^2 + k }, the axis of symmetry is given by the equation \text{ x = h }. In our example function \(f(x) = (x+3)^2 - 2\), we identified \(h = -3\). Therefore, the axis of symmetry is \text{ x = -3 }.This line is crucial when graphing because it shows where the parabola turns. Every point on one side of the axis has a corresponding point on the other side. Understanding the axis helps in accurately drawing the shape of the parabola.
Minimum Value of a Quadratic Function
For quadratic functions that open upwards (\(a > 0\)), the vertex represents the minimum point of the parabola. The minimum value is simply the \(y\)-coordinate of the vertex. The general form of our quadratic function is \text{ f(x) = a(x-h)^2 + k }.The minimum value is \text{ k }In the function \(f(x) = (x+3)^2 - 2\), we already determined that \(k = -2\). Thus, the minimum value of the function is \(-2\). Knowing where the minimum value is helps in understanding the range of the quadratic function and constraints in practical problems.
Graphing Parabolas
Graphing a parabola involves several steps, starting with identifying key features from the vertex form of the function. These steps include:
- Identify the vertex \((h, k)\). For \(f(x) = (x+3)^2 - 2\), it’s \((-3, -2)\).
- Draw the axis of symmetry, which is the line \(x = h\). Here, \(x = -3\).
- Plot the vertex on the coordinate plane.
- Determine the direction of the parabola. Since \(a > 0\), it opens upwards.
- Identify additional points on either side of the axis by choosing \(x eq h\) values.
- Plot these points and draw the parabola shape, ensuring symmetry.