Chapter 3: Problem 38
Find the maximum or minimum value of the function. $$f(x)=6 x^{2}-24 x-100$$
Short Answer
Expert verified
The minimum value of the function is \(-124\), at \( x = 2 \).
Step by step solution
01
Identify the Form of the Function
The function given is a quadratic function, expressed in the standard form \( f(x) = ax^2 + bx + c \). For this function, \( a = 6 \), \( b = -24 \), and \( c = -100 \). A quadratic function has a parabola shape, and since \( a > 0 \), the parabola opens upwards and therefore has a minimum point.
02
Use Vertex Formula to Find Vertex
The vertex of a parabola \( ax^2 + bx + c \) is given by the formula \( x = -\frac{b}{2a} \). Substitute \( a = 6 \) and \( b = -24 \) to find the x-coordinate of the vertex: \[ x = -\frac{-24}{2 \times 6} = \frac{24}{12} = 2 \]
03
Calculate the Minimum Value at the Vertex
Now, substitute \( x = 2 \) back into the function to find the function value at this x-coordinate, which will be the minimum value: \[ f(2) = 6(2)^2 - 24(2) - 100 \] Calculate step by step: \[ f(2) = 6 \times 4 - 48 - 100 = 24 - 48 - 100 \] \[ f(2) = 24 - 48 - 100 = -124 \]
04
Conclusion
The minimum value of the function \( f(x) = 6x^2 - 24x - 100 \) is \(-124\), occurring at \( x = 2 \). This is because the parabola opens upwards and the vertex represents the lowest point on the graph.
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Parabola
A quadratic function is often associated with the graph of a parabola. This is because when you plot a quadratic equation, the shape that emerges is that of a U or an upside-down U, depending on the sign of the coefficient of the quadratic term. Here are some key features of a parabola:
- The highest or lowest point on a parabola is called the vertex.
- If the coefficient of the quadratic term (\(a\)) is positive, the parabola opens upwards and looks like a U shape.
- If \(a\) is negative, the parabola opens downwards, creating an upside-down U shape.
Vertex Formula
The vertex of a parabola is a crucial point because it represents either the minimum or maximum value of the function. To locate this vertex, we use the vertex formula. For a quadratic function given by \(ax^2 + bx + c\), the x-coordinate of the vertex can be calculated using the formula:\[ x = -\frac{b}{2a} \]Let's break it down further:
- The calculation involves the coefficients \(b\) and \(a\) from the standard quadratic form.
- In the formula \(x = -\frac{-24}{2 \times 6}\), substituting the values \(b = -24\) and \(a = 6\) gives the x-coordinate of the vertex as \(x = 2\).
Minimum Value
Once the vertex is located, the next step is to find the minimum or maximum value of the function, depending on the direction of the parabola. For a parabola that opens upwards, like the one described by \(f(x) = 6x^2 - 24x - 100\), the vertex is the minimum point.Here's how to compute this minimum value:
- With the x-coordinate of the vertex known to be \(x = 2\), substitute this back into the original equation to find \(f(2)\).
- Calculating step by step, \(f(2) = 6(2)^2 - 24 \times 2 - 100\)
- This simplifies to \(f(2) = 6 \times 4 - 48 - 100 = -124\).