Chapter 5: Problem 41
Sketch the graph of the line satisfying the given conditions. Passing through \((1,-2)\) with slope \(\frac{-2}{3}\)
Short Answer
Expert verified
The line passes through \(1, -2\) with a slope of \(\frac{-2}{3}\). Equation: \(y = \frac{-2}{3}x - \frac{4}{3}\).
Step by step solution
01
Identify given information
The given point is \(1, -2\), and the slope of the line is \(\frac{-2}{3}\text{\)}.
02
Use point-slope form
The point-slope form of the equation of a line is \(y - y_1 = m(x - x_1)\), where \((x_1, y_1)\) is the given point and \m\ is the slope. Substitute the values: \(y + 2 = \frac{-2}{3}(x - 1)\).
03
Distribute and simplify
Distribute the slope on the right side: \(y + 2 = \frac{-2}{3}x + \frac{2}{3}\).
04
Isolate y
Subtract 2 from both sides to isolate \y\: \(y = \frac{-2}{3}x + \frac{2}{3} - 2\).\text{Convert } -2 \text{ to} \ \frac{-6}{3}\ \text{and simplify the y-intercept term.} \(y = \frac{-2}{3}x - \frac{4}{3}\).This is the slope-intercept form.
05
Plot the given point
Mark the point \(1, -2\) on the graph.
06
Use slope to find another point
From point \(1, -2\), use the slope \(\frac{-2}{3}\text{\)} to plot another point: move 3 units to the right \ and 2 units down to reach \(4, -4\).
07
Draw the line
Draw a straight line passing through the points \((1, -2)\) and \((4, -4)\).
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Point-Slope Form of a Linear Equation
The point-slope form is very useful for writing an equation when you have a point and the slope of the line. It is given by the formula: \( y - y_1 = m(x - x_1) \). Here,
- \( (x_1, y_1) \) are the coordinates of the given point
- \( m \) is the slope of the line
Slope-Intercept Form of a Linear Equation
The slope-intercept form is another popular way to write the equation of a line. Its formula is \( y = mx + b \), where
Starting from \( y + 2 = \frac{-2}{3}(x - 1) \), distribute the \( \frac{-2}{3} \) on the right side:
\( y + 2 = \frac{-2}{3}x + \frac{2}{3} \)
Subtract 2 from both sides to isolate \( y \):
\( y = \frac{-2}{3}x + \frac{2}{3} - 2 \)
To simplify, convert \( -2 \) to a fraction with the same denominator:
\( -2 = \frac{-6}{3} \)
Simplifying further, you'll get:\( y = \frac{-2}{3}x - \frac{4}{3} \). Now the equation is in slope-intercept form.
- \( m \) is the slope
- \( b \) is the y-intercept (where the line crosses the y-axis)
Starting from \( y + 2 = \frac{-2}{3}(x - 1) \), distribute the \( \frac{-2}{3} \) on the right side:
\( y + 2 = \frac{-2}{3}x + \frac{2}{3} \)
Subtract 2 from both sides to isolate \( y \):
\( y = \frac{-2}{3}x + \frac{2}{3} - 2 \)
To simplify, convert \( -2 \) to a fraction with the same denominator:
\( -2 = \frac{-6}{3} \)
Simplifying further, you'll get:\( y = \frac{-2}{3}x - \frac{4}{3} \). Now the equation is in slope-intercept form.
Plotting Points on a Graph
Plotting points is a fundamental skill in graphing linear equations. Each point has coordinates \( (x, y) \). For example, the point \( (1, -2) \) means you go 1 unit to the right (along the x-axis) and 2 units down (along the y-axis). To plot this point on a graph:
- Start from the origin \( (0, 0) \)
- Move 1 unit to the right
- Move 2 units down
Calculating Slope
The slope of a line tells us how steep the line is. It is calculated as the 'rise' over the 'run' between two points on the line. The formula is: \[ m = \frac{y_2 - y_1}{x_2 - x_1} \] Where:
\( m = \frac{-4 - (-2)}{4 - 1} = \frac{-4 + 2}{4 - 1} = \frac{-2}{3} \). This tells us that for every 3 units we move to the right, we move 2 units down.
- \( (x_1, y_1) \) and \( (x_2, y_2) \) are two points on the line
\( m = \frac{-4 - (-2)}{4 - 1} = \frac{-4 + 2}{4 - 1} = \frac{-2}{3} \). This tells us that for every 3 units we move to the right, we move 2 units down.
Graphing Linear Equations
Graphing linear equations involves plotting points and drawing a straight line through them. To graph a line based on its equation:
- Convert the equation to slope-intercept form to identify the slope and y-intercept
- Plot the y-intercept on the y-axis
- Use the slope to find another point starting from the y-intercept
- Draw a straight line through the points
- The y-intercept is \( - \frac{4}{3}\), i.e., mark the point \( (0, - \frac{4}{3}) \)
- From this point, use the slope \( \frac{-2}{3} \) to find another point, i.e., move 3 units right and 2 units down