Chapter 1: Problem 71
For the following exercises, write the equation of the line satisfying the given conditions in slope-intercept form. Passing through \((2,1)\) and \((-2,-1)\)
Short Answer
Expert verified
The equation is \( y = \frac{1}{2}x \).
Step by step solution
01
Identify the Slope Formula
The slope-intercept form of a line’s equation is \( y = mx + b \), where \( m \) is the slope and \( b \) is the y-intercept. First, we need to find the slope (\( m \)). The formula for the slope between two points \( (x_1, y_1) \) and \( (x_2, y_2) \) is \( m = \frac{y_2 - y_1}{x_2 - x_1} \).
02
Substitute Values into the Slope Formula
Plug the given points \((2,1)\) and \((-2,-1)\) into the slope formula: \( m = \frac{-1 - 1}{-2 - 2} \). Simplify the expression to find the slope.
03
Calculate the Slope
Perform the calculations: \( m = \frac{-2}{-4} = \frac{1}{2} \). The slope of the line is \( \frac{1}{2} \).
04
Use the Point-Slope Form to Find the Y-Intercept
The point-slope form of a line’s equation is \( y - y_1 = m(x - x_1) \). Use point \((2,1)\) and slope \( \frac{1}{2} \): \( y - 1 = \frac{1}{2}(x - 2) \).
05
Convert to Slope-Intercept Form
Simplify the equation \( y - 1 = \frac{1}{2}(x - 2) \) to get \( y = \frac{1}{2}x - 1 + 1 \). This simplifies further to \( y = \frac{1}{2}x \).
06
Conclusion
The slope-intercept form of the line passing through the points \((2,1)\) and \((-2,-1)\) is \( y = \frac{1}{2}x \).
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Slope-Intercept Form
One of the most common ways to express the equation of a line is through the slope-intercept form. It is written as \( y = mx + b \), where \( m \) represents the slope of the line and \( b \) denotes the y-intercept, which is the point where the line crosses the y-axis. This form is especially helpful because it provides direct information about the line's direction and y-intercept.
- **Slope**: The value of \( m \) tells us how steep the line is, as well as its direction. A positive slope means the line is increasing, while a negative slope indicates a decreasing line.
- **Y-Intercept**: The coefficient \( b \) gives the y-coordinate at which the line crosses the y-axis. This means if \( x = 0 \), then \( y = b \).
Point-Slope Form
The point-slope form is particularly useful for quickly writing equations of lines when you know one point on the line and its slope. This form looks like \( y - y_1 = m(x - x_1) \), where \( m \) is the slope and \( (x_1, y_1) \) are the coordinates of the point through which the line passes.
- **Derived information**: Unlike slope-intercept form, we begin here with the slope \( m \) and a specific point to find the equation of the line.
- **Flexibility**: It's great for developing an equation quickly, especially when only a point and a slope are given.
Slope Formula
The slope formula defines the steepness and the direction of a line between two points. Given two points on a line, \((x_1, y_1)\) and \((x_2, y_2)\), the formula is \( m = \frac{y_2 - y_1}{x_2 - x_1} \).
- **Difference in y-coordinates**: The numerator \( y_2 - y_1 \) determines the change in the vertical direction.
- **Difference in x-coordinates**: The denominator \( x_2 - x_1 \) signifies the change in the horizontal direction.