Chapter 0: Problem 7
(a) write the linear function \(f\) such that it has the indicated function values and (b) sketch the graph of the function. $$ f\left(\frac{1}{2}\right)=-6, f(4)=-3 $$
Short Answer
Expert verified
The equation of the function is \(f(x) = \frac{6}{7}x - \frac{6.42857}\). This would result in a straight line graph with slope \(\frac{6}{7}\) and y-intercept -\frac{6.42857}.
Step by step solution
01
Determine the Slope
The slope of a linear function can be determined using the formula \(m = \frac{y_2 - y_1}{x_2 - x_1}\). Given that \(f(\frac{1}{2}) = -6\) and \(f(4) = -3\), this gives two points on the line: (\(\frac{1}{2}, -6) and (4, -3). Using these, the slope is calculated as: \(m = \frac{-3 - (-6)}{4 - \frac{1}{2}} = \frac{3}{\frac{7}{2}} = \frac{6}{7}\).
02
Solve for the Y-intercept
The y-intercept (b) of a linear function can be found using the formula \(b = y - mx\), where m is the slope and the pair (x, y) is any point on the line. Using the point (\(\frac{1}{2}, -6) and the slope \(\frac{6}{7}\), one can calculate the y-intercept as: \(b = -6 - \frac{6}{7}*\frac{1}{2} = -\frac{42}{7} - \frac{3}{7} = -\frac{45}{7} = -\frac{6.42857}\).
03
Write the Equation of the Line
The equation of a line can be written in the form \(y = mx + b\), where m is the slope and b is the y-intercept. Using the slope of \(\frac{6}{7}\) and y-intercept of -\frac{6.42857}, the equation of the function f(x) can be written as \(f(x) = \frac{6}{7}x - \frac{6.42857}\).
04
Sketch the Graph
For sketching the graph, mark the y-intercept on the y-axis at -\frac{6.42857} and the rise-over-run using the slope of \(\frac{6}{7}\). First get up 6 units (as positive 6 is the numerator) and then move to the right by 7 units (as 7 is the denominator of the slope) to mark another point on the graph. Then use a ruler to draw a straight line passing through the marked points.
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Slope Calculation
To find the slope of a linear function, we use the formula \( m = \frac{y_2 - y_1}{x_2 - x_1} \). This formula is all about determining how steep the line is. In simpler terms, the slope tells you how much the function value (or \( y \)) changes for a given change in \( x \).
For example, in our exercise, we have two points: \( \left( \frac{1}{2}, -6 \right) \) and \( (4, -3) \). The slope \( m \) can be calculated by plugging these points into the formula:
For example, in our exercise, we have two points: \( \left( \frac{1}{2}, -6 \right) \) and \( (4, -3) \). The slope \( m \) can be calculated by plugging these points into the formula:
- Subtract the \( y \)-values: \( -3 - (-6) = 3 \)
- Subtract the \( x \)-values: \( 4 - \frac{1}{2} = \frac{7}{2} \)
Y-Intercept
The y-intercept is the point where the line crosses the y-axis. It’s denoted as \( b \) in the equation of a line \( y = mx + b \). To find \( b \), you can use the formula \( b = y - mx \), where \( m \) is the slope, and \( (x, y) \) is any known point on the line.
Given one of our points \( \left( \frac{1}{2}, -6 \right) \), we can substitute \( m = \frac{6}{7} \) and solve for \( b \):
Given one of our points \( \left( \frac{1}{2}, -6 \right) \), we can substitute \( m = \frac{6}{7} \) and solve for \( b \):
- Start with \( -6 - \frac{6}{7} \times \frac{1}{2} \)
- Calculate \( b \): \( -\frac{42}{7} - \frac{3}{7} = -\frac{45}{7} \)
- \( b \) is approximately \( -6.42857 \)
Graphing Linear Equations
Graphing linear equations is like connecting dots on a plane to visualize a function. Start by plotting the y-intercept on the y-axis. For our function, this is \( b = -6.42857 \), which is slightly below -6.5 on the y-axis.
Next, use the slope \( \frac{6}{7} \) to determine another point. Move up (rise) by 6 units from the y-intercept, and then to the right (run) by 7 units. Mark this second point.
Next, use the slope \( \frac{6}{7} \) to determine another point. Move up (rise) by 6 units from the y-intercept, and then to the right (run) by 7 units. Mark this second point.
- Begin by plotting the point at \( (0, -6.42857) \)
- From this point, move up 6, right 7 to find another point
- Draw a line through these points with a ruler for precision
Writing Linear Equations
Writing linear equations in the form \( y = mx + b \) is putting together the slope and y-intercept to describe the function completely. Once you have these two values, assembling the equation is straightforward. For our exercise, we found:
This equation tells us that for any value of \( x \), we can find \( y \) by multiplying \( x \) by \( \frac{6}{7} \) and then subtracting 6.42857. Practicing writing these equations helps in understanding how changes in the slope or y-intercept affect the graph.
- The slope \( m = \frac{6}{7} \)
- The y-intercept \( b = -6.42857 \)
This equation tells us that for any value of \( x \), we can find \( y \) by multiplying \( x \) by \( \frac{6}{7} \) and then subtracting 6.42857. Practicing writing these equations helps in understanding how changes in the slope or y-intercept affect the graph.