Table of contents
- 0. Review of Algebra4h 18m
- 1. Equations & Inequalities3h 18m
- 2. Graphs of Equations1h 43m
- 3. Functions2h 17m
- 4. Polynomial Functions1h 44m
- 5. Rational Functions1h 23m
- 6. Exponential & Logarithmic Functions2h 28m
- 7. Systems of Equations & Matrices4h 5m
- 8. Conic Sections2h 23m
- 9. Sequences, Series, & Induction1h 22m
- 10. Combinatorics & Probability1h 45m
2. Graphs of Equations
Lines
Problem 44
Textbook Question
In Exercises 41–44, use the given conditions to write an equation for each line in point-slope form and slope-intercept form. Passing through (-3, 6) and perpendicular to the line whose equation is y = (1/3)x + 4
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Identify the slope of the given line y = (1/3)x + 4. The slope is the coefficient of x, which is 1/3.
Recall that perpendicular lines have slopes that are negative reciprocals of each other. The negative reciprocal of 1/3 is -3. Therefore, the slope of the desired line is -3.
Use the point-slope form of a line equation: y - y₁ = m(x - x₁), where m is the slope and (x₁, y₁) is a point on the line. Substitute m = -3 and the point (-3, 6) into the formula: y - 6 = -3(x + 3).
Simplify the point-slope form equation if needed. For example, distribute the slope -3 to the terms inside the parentheses: y - 6 = -3x - 9.
Convert the equation to slope-intercept form (y = mx + b) by isolating y. Add 6 to both sides: y = -3x - 9 + 6, which simplifies to y = -3x - 3.
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Point-Slope Form
Point-slope form is a way to express the equation of a line using a specific point on the line and its slope. The formula is given by y - y1 = m(x - x1), where (x1, y1) is a point on the line and m is the slope. This form is particularly useful for quickly writing the equation of a line when you know a point and the slope.
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Point-Slope Form
Slope-Intercept Form
Slope-intercept form is another way to express the equation of a line, defined as y = mx + b, where m is the slope and b is the y-intercept. This form allows for easy identification of the slope and where the line crosses the y-axis. Converting from point-slope to slope-intercept form is a common task in algebra.
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Slope-Intercept Form
Perpendicular Lines
Two lines are perpendicular if the product of their slopes is -1. This means that if one line has a slope of m, the slope of a line perpendicular to it will be -1/m. Understanding this relationship is crucial for finding the slope of a line that is perpendicular to a given line, which is necessary for solving the problem at hand.
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Parallel & Perpendicular Lines
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Related Practice
Textbook Question
The graph of a linear function f is shown. (a) Identify the slope, y-intercept, and x-intercept. (b) Write an equation that defines f.
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