Chapter 2: Problem 66
Find the equation of the line that passes through the following points: \((2 a, b)\) and \((a, b+1)\)
Short Answer
Expert verified
The equation of the line is \( y = -\frac{1}{a}x + (b + 2) \).
Step by step solution
01
Identify the Slope Formula
The formula for the slope (m) of a line passing through two points \((x_1, y_1)\) and \((x_2, y_2)\) is given by:\[ m = \frac{y_2 - y_1}{x_2 - x_1} \]
02
Substitute the Given Points into the Slope Formula
The coordinates of the points are \((x_1, y_1) = (2a, b)\) and \((x_2, y_2) = (a, b+1)\).Substitute these values into the slope formula:\[ m = \frac{(b+1) - b}{a - 2a} = \frac{1}{-a} = -\frac{1}{a} \]
03
Use the Point-Slope Form of a Line
The point-slope form equation of a line is:\[ y - y_1 = m(x - x_1) \]You can use either of the given points. Choose the point \((2a, b)\):\[ y - b = -\frac{1}{a}(x - 2a) \]
04
Simplify the Equation
Distribute the slope in the equation:\[ y - b = -\frac{1}{a}x + 2 \]Rearrange it to the standard form by adding b to both sides:\[ y = -\frac{1}{a}x + 2 + b \]
05
Write the Final Equation in Slope-Intercept Form
Combine constants on the right side:\( y = -\frac{1}{a}x + (b + 2) \) which is the equation of the line in slope-intercept form \( y = mx + c \).
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Slope Formula
The slope formula is essential for finding the steepness or incline of a line that connects two given points. This formula is written as: \[ m = \frac{y_2 - y_1}{x_2 - x_1} \] where \( m \) represents the slope, \( (x_1, y_1) \) and \( (x_2, y_2) \) are the coordinates of the two points.Understanding the slope gives insight into how much the line rises or falls as it moves from one point to another.
- A positive slope indicates the line ascends when moving from left to right.
- A negative slope suggests the line descends as it goes from left to right.
- A zero slope means the line is horizontal, implying no rise.
- An undefined slope is the indication of a vertical line.
Point-Slope Form
The point-slope form is a technique used to write the equation of a line when you know its slope and a point on the line. The general representation is given by:\[ y - y_1 = m(x - x_1) \]where \((x_1, y_1)\) is the point on the line, and \( m \) is the slope.This form is particularly helpful because it directly ties the equation to a specific point and the slope, making it easy to understand graphically how the line behaves.
- You have the freedom to choose any point from the two given points.
- This form helps you transition into other forms like slope-intercept form easily.
Slope-Intercept Form
The slope-intercept form is possibly the most popular and straightforward form of a linear equation:\[ y = mx + c \]where \( m \) stands for the slope and \( c \) represents the y-intercept of the line.This form clearly shows the slope of the line and where it intersects the y-axis, making it extremely beneficial when graphing or comparing lines.
- Easy to plot on a coordinate plane—just start at the y-intercept \( c \) and follow the slope \( m \).
- Great for quickly identifying parallel or perpendicular lines by comparing slopes.