Chapter 3: Problem 35
Find an equation of the line passing through each pair of points. Write the equation in the form \(A x+B y=C .\) See Example 5. $$ (2,3) \text { and }(-1,-1) $$
Short Answer
Expert verified
The equation of the line is \(4x - 3y = -1\).
Step by step solution
01
Identify the formula for the slope between two points
The formula for calculating the slope \( m \) between two points \((x_1, y_1)\) and \((x_2, y_2)\) is given by: \[ m = \frac{y_2 - y_1}{x_2 - x_1} \] In this case, the points are \((2, 3)\) and \((-1, -1)\). We will use this formula to find the slope.
02
Calculate the slope
Substitute the coordinates \((x_1, y_1) = (2, 3)\) and \((x_2, y_2) = (-1, -1)\) into the slope formula: \[ m = \frac{-1 - 3}{-1 - 2} = \frac{-4}{-3} = \frac{4}{3} \] The slope of the line is \( \frac{4}{3} \).
03
Use point-slope formula to find equation of the line
We use the point-slope form of the equation, which is given by: \[ y - y_1 = m(x - x_1) \] Using the point \((2, 3)\) and the slope \( \frac{4}{3} \), we substitute into the equation: \[ y - 3 = \frac{4}{3}(x - 2) \]
04
Simplify the point-slope equation to standard form
First, simplify the point-slope equation: \[ y - 3 = \frac{4}{3}x - \frac{8}{3} \] Add 3 to both sides: \[ y = \frac{4}{3}x - \frac{8}{3} + \frac{9}{3} \] \[ y = \frac{4}{3}x + \frac{1}{3} \] Now we convert this to the standard form: Multiply through by 3 to eliminate fractions: \[ 3y = 4x + 1 \] Rearrange to get \(Ax + By = C\) form: \[ 4x - 3y = -1 \]
05
Write the final equation in standard form
The standard form of the line's equation is \( 4x - 3y = -1 \). This represents the line passing through points (2,3) and (-1,-1).
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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, typically represented by the letter \( m \). It indicates how much the line rises or falls as you move from left to right. Finding the slope involves using the formula:
- \( m = \frac{y_2 - y_1}{x_2 - x_1} \)
- \( m = \frac{-1 - 3}{-1 - 2} = \frac{4}{3} \)
Point-Slope Form
The point-slope form is a convenient way to express the equation of a line using one of its points, alongside its slope. The equation is structured as:
- \( y - y_1 = m(x - x_1) \)
- Given point: \((2, 3)\)
- Slope: \( \frac{4}{3} \)
- \( y - 3 = \frac{4}{3}(x - 2) \)
Standard Form of a Line
The standard form of a line's equation is a powerful tool, especially in situations where you need a uniform representation of multiple lines. Its format is:
- \( Ax + By = C \)
- Started with: \( y = \frac{4}{3}x + \frac{1}{3} \)
- Eliminate fractions: \( 3y = 4x + 1 \)
- Rearrange to: \( 4x - 3y = -1 \)