Chapter 2: Problem 76
Find a function whose graph is the given curve. The line segment joining the points \((-3,-2)\) and \((6,3)\)
Short Answer
Expert verified
The equation of the line is \( y = \frac{5}{9}x - \frac{1}{3} \).
Step by step solution
01
Identify the form of the function
Lines on a graph can be represented using the linear equation formula, which is given by: \( y = mx + c \), where \( m \) is the slope, and \( c \) is the y-intercept.
02
Calculate the slope \( m \)
The slope \( m \) of a line between two points \((x_1, y_1)\) and \((x_2, y_2)\) is given by the formula: \( m = \frac{y_2 - y_1}{x_2 - x_1} \). Substitute the given points \((-3, -2)\) and \((6, 3)\) into the formula: \[ m = \frac{3 - (-2)}{6 - (-3)} = \frac{3 + 2}{6 + 3} = \frac{5}{9} \]
03
Use the point-slope form to find the equation
We use the point-slope form of the line equation to find \( c \). The point-slope form is \( y - y_1 = m(x - x_1) \). Let's choose point \((-3, -2)\) for our calculations:\[ y - (-2) = \frac{5}{9}(x - (-3)) \]\[ y + 2 = \frac{5}{9}(x + 3) \]
04
Simplify the equation
Expand and simplify the equation from Step 3:\[ y + 2 = \frac{5}{9}x + \frac{5}{3} \]Subtract 2 from both sides:\[ y = \frac{5}{9}x + \frac{5}{3} - 2 \]Convert -2 into fractional form to combine:\[ y = \frac{5}{9}x + \frac{5}{3} - \frac{6}{3} \]\[ y = \frac{5}{9}x - \frac{1}{3} \]
05
Verify the function with both points
To confirm that our function works, plug in both points to verify:For \((-3, -2)\):\( y = \frac{5}{9}(-3) - \frac{1}{3} = -\frac{15}{9} - \frac{1}{3} = -\frac{20}{9} = -2 \)For \((6, 3)\):\( y = \frac{5}{9}(6) - \frac{1}{3} = \frac{30}{9} - \frac{1}{3} = 3 \)Both points satisfy the function
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Slope of a Line
The slope of a line is a measure of its steepness and direction. It is represented by the letter \( m \) in the linear equation \( y = mx + c \). Calculating the slope involves taking two points on the line, such as \((-3, -2)\) and \((6, 3)\), and using the formula \( m = \frac{y_2 - y_1}{x_2 - x_1} \). By substituting the coordinates into this formula, we find the slope:
- Calculate the difference in \( y \)-coordinates: \( 3 - (-2) = 3 + 2 = 5 \)
- Calculate the difference in \( x \)-coordinates: \( 6 - (-3) = 6 + 3 = 9 \)
- Divide the differences: \( \frac{5}{9} \)
Point-Slope Form
The point-slope form is a handy equation used to easily find the equation of a line when you have a point on the line and its slope. It is written as \( y - y_1 = m(x - x_1) \). This can help simplify finding the line’s equation without first finding its y-intercept. For example, using the point \((-3, -2)\) and slope \( \frac{5}{9} \), the setup is:
- Plug into formula: \( y - (-2) = \frac{5}{9}(x - (-3)) \)
- Simplify to \( y + 2 = \frac{5}{9}(x + 3) \)
Y-Intercept
The y-intercept is the point where the line crosses the y-axis, denoted as \( c \) in the equation \( y = mx + c \). To find it, you adjust the point-slope form by removing any constants on the left side through algebraic manipulation.
- Start with: \( y + 2 = \frac{5}{9}x + \frac{5}{3} \)
- Subtract \( 2 \): \( y = \frac{5}{9}x + \frac{5}{3} - 2 \)
- Convert to common fractions: \( y = \frac{5}{9}x + \frac{5/3} - \frac{6/3} \)
- Result: \( y = \frac{5}{9}x - \frac{1}{3} \)
Graph of a Line
Graphing a line starts with plotting its equation, allowing us to see its trajectory and intersection points. With the equation \( y = \frac{5}{9}x - \frac{1}{3} \), observe its key features:
- Slope \( \frac{5}{9} \) means a gentle upward incline—\( 5 \) units up for \( 9 \) units along the x-axis.
- The y-intercept, where it crosses the y-axis, is at \( -\frac{1}{3} \).
- Begin at the y-intercept \((-\frac{1}{3})\) on the y-axis.
- From the intercept, use the slope to determine points along the line. Move right \( 9 \) units, then up \( 5 \) units to plot another point.
- Draw a straight line through the points to extend it in both directions.