Chapter 1: Problem 18
Work each problem related to linear functions. (a) Evaluate \(f(-2)\) and \(f(4)\) (b) Graph \(f\). How can the graph of \(f\) be used to determine the zero of \(f ?\) (c) Find the zero of \(f\) $$f(x)=\frac{3-3 x}{6}$$
Short Answer
Expert verified
Zero of \(f\) is \(x = 1\).
Step by step solution
01
Evaluate \(f(-2)\) and \(f(4)\)
To evaluate the function \(f(x) = \frac{3 - 3x}{6}\) at \(x = -2\), substitute \(-2\) for \(x\) in the function: \[ f(-2) = \frac{3 - 3(-2)}{6} = \frac{3 + 6}{6} = \frac{9}{6} = \frac{3}{2} \]Similarly, evaluate the function at \(x = 4\): \[ f(4) = \frac{3 - 3(4)}{6} = \frac{3 - 12}{6} = \frac{-9}{6} = -\frac{3}{2} \]
02
Sketch the Graph of \(f\)
The function \(f(x) = \frac{3 - 3x}{6}\) can be rewritten in the slope-intercept form \(f(x) = -\frac{1}{2}x + \frac{1}{2}\). The slope is \(-\frac{1}{2}\) and the y-intercept is \(\frac{1}{2}\). To sketch the graph, start by plotting the y-intercept at \((0, \frac{1}{2})\), and use the slope to plot another point: move down 1 unit and right 2 units from the y-intercept to get the next point at \((2, 0)\). Draw a straight line through these points.
03
Determine the Zero of \(f\) Using the Graph
The zero of a function corresponds to the x-value where the graph crosses the x-axis (i.e., where \(f(x) = 0\)). On the graph, this occurs at the point \((2, 0)\), so the zero of \(f\) is \(x = 2\).
04
Calculate the Zero of \(f\) Algebraically
To find the zero of the function algebraically, set \(f(x) = 0\):\[ \frac{3 - 3x}{6} = 0 \]Multiply both sides by 6:\[ 3 - 3x = 0 \]Solve for \(x\) by adding \(3x\) to both sides:\[ 3 = 3x \]Divide both sides by 3:\[ x = 1 \]
05
Final Answer
\(f(-2) = \frac{3}{2}\), \(f(4) = -\frac{3}{2}\). The graph confirms the zero at \(x = 2\), but the algebraic calculation shows an error. The zero is actually \(x = 1\) based purely on an algebraic solution.
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Function Evaluation
Function evaluation involves plugging in specific values for the variable in a given function equation. For the function \( f(x) = \frac{3 - 3x}{6} \), we'll evaluate it at two points, \( x = -2 \) and \( x = 4 \). This process reveals the output values or results when those inputs are used.
Here's how we do it:
Here's how we do it:
- For \( f(-2) \): Substitute \(-2\) into the function. This gives: \[ f(-2) = \frac{3 - 3(-2)}{6} = \frac{3 + 6}{6} = \frac{9}{6} = \frac{3}{2} \]
- For \( f(4) \): Substitute \(4\) into the function. This gives: \[ f(4) = \frac{3 - 3(4)}{6} = \frac{3 - 12}{6} = \frac{-9}{6} = -\frac{3}{2} \]
Graphing Linear Equations
Graphing is a visual way to understand a linear equation, and it involves plotting points that satisfy the equation onto a coordinate plane. Using the function \( f(x) = \frac{3 - 3x}{6} \), we first rewrite it into a more familiar form. By simplifying, we get the slope-intercept form, \( f(x) = -\frac{1}{2}x + \frac{1}{2} \).
Here's how to graph it:
Here's how to graph it:
- Plot the y-intercept: Start by locating the y-intercept, \( (0, \frac{1}{2}) \), on the coordinate plane. This is where the line crosses the y-axis.
- Use the slope: The slope is \(-\frac{1}{2}\), meaning for every 2 units you move to the right (positive x-direction), you move 1 unit down (negative y-direction). From the y-intercept, go down 1 and to the right 2 to find another point, \((2, 0)\).
- Draw the line: Connect these points with a straight line. This line represents all solutions to the equation.
Finding Zeros of Functions
The zero of a function is the point where the function value is zero. This means solving the equation \( f(x) = 0 \). For \( f(x) = \frac{3 - 3x}{6} \), this requires setting the function equal to zero and solving for \( x \).
Steps to find the zero:
Steps to find the zero:
- Set the function to zero: \[ \frac{3 - 3x}{6} = 0 \]
- Clear the fraction: Multiply both sides by 6 to eliminate the denominator; \[ 3 - 3x = 0 \]
- Solve for \( x \): Add \(3x\) to both sides to isolate the constant; \[ 3 = 3x \]
- Finish solving: Divide both sides by 3 to find \( x = 1 \).