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Ch. 2 - Functions and Graphs
Blitzer - College Algebra 8th Edition
Blitzer8th EditionCollege AlgebraISBN: 9780136970514Not the one you use?Change textbook
Chapter 3, Problem 30

Use the given conditions to write an equation for each line in point-slope form and slope-intercept form. Passing through (−2, −4) and (1, −1)

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Identify the two given points: \((-2, -4)\) and \((1, -1)\).
Calculate the slope \(m\) using the formula \(m = \frac{y_2 - y_1}{x_2 - x_1}\), where \((x_1, y_1) = (-2, -4)\) and \((x_2, y_2) = (1, -1)\).
Use the point-slope form of a line equation: \(y - y_1 = m(x - x_1)\), substituting \(m\) and one of the points (either \((-2, -4)\) or \((1, -1)\)).
Simplify the point-slope form equation if needed, but keep it in the form \(y - y_1 = m(x - x_1)\) for the point-slope form answer.
Convert the point-slope form to slope-intercept form \(y = mx + b\) by solving for \(y\) and simplifying the expression.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Slope of a Line

The slope measures the steepness of a line and is calculated as the change in y-values divided by the change in x-values between two points. For points (x₁, y₁) and (x₂, y₂), slope m = (y₂ - y₁) / (x₂ - x₁). It is essential for writing the equation of a line.
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The Slope of a Line

Point-Slope Form of a Line

Point-slope form expresses a line's equation using a known point (x₁, y₁) and the slope m: y - y₁ = m(x - x₁). This form is useful when you know a point on the line and its slope, allowing you to write the equation directly.
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Point-Slope Form

Slope-Intercept Form of a Line

Slope-intercept form is y = mx + b, where m is the slope and b is the y-intercept. After finding the slope and using a point to solve for b, this form clearly shows the line's slope and where it crosses the y-axis.
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Graphing Lines in Slope-Intercept Form