Chapter 4: Problem 12
Find the slope of the line through the first two points given. Assume the third point is also on the line and find the missing coordinate. a. \((-1,5)\) and \((3,1) ;(5, \square)\) b. \((2,-5)\) and \((2,-2) ;(\square, 3)\) c. \((-10,22)\) and \((-2,2) ;(\square,-3)\)
Short Answer
Expert verified
a: -1; b: 2; c: -4/5
Step by step solution
01
Find the Slope (a)
The formula for the slope between two points \((x_1, y_1)\) and \((x_2, y_2)\) is \( m = \frac{y_2 - y_1}{x_2 - x_1} \). For points \((-1, 5)\) and \((3, 1)\), the slope is \( m = \frac{1 - 5}{3 - (-1)} = \frac{-4}{4} = -1 \).
02
Use the Slope to Find the Missing Coordinate (a)
Using the point-slope form of the equation of a line, \( y - y_1 = m(x - x_1) \), we substitute one of the known points, say \((3, 1)\), and the slope \(-1\) to get: \( y - 1 = -1(x - 3) \). Simplifying, \( y = -x + 4 \). For point \((5, \square)\), set \(x = 5\) to get \( y = -5 + 4 = -1 \). So, the missing coordinate is \(-1\).
03
Find the Slope (b)
The slope between points \((2, -5)\) and \((2, -2)\) is undefined because both points have the same x-coordinate. This indicates a vertical line, so all points have the same x-coordinate. The missing coordinate for point \((\square, 3)\) is also \(2\). The coordinate is \(2\).
04
Find the Slope (c)
Calculate the slope for points \((-10, 22)\) and \((-2, 2)\) using the formula \( m = \frac{y_2 - y_1}{x_2 - x_1} \). Here, \( m = \frac{2 - 22}{-2 - (-10)} = \frac{-20}{8} = -\frac{5}{2} \).
05
Use the Slope to Find the Missing Coordinate (c)
Using point-slope form with point \((-2, 2)\) and slope \(-\frac{5}{2}\), we have \( y - 2 = -\frac{5}{2}(x + 2) \). Distributing and simplifying, \( y = -\frac{5}{2}x - 5 \). For point \((\square, -3)\), set \( y = -3 \): \(-3 = -\frac{5}{2}x - 5 \). Solving for \(x\), add 5 to both sides: \(2 = -\frac{5}{2}x\). Multiply both sides by \(-\frac{2}{5}\) to get \(x = -\frac{4}{5}\).
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Linear Equations
Linear equations describe lines on a graph using a simple algebraic formula. Each linear equation can be written in different forms, such as the standard form, slope-intercept form, and point-slope form.
A linear equation in the slope-intercept form, for example, looks like this:
By identifying the slope and y-intercept, you can quickly sketch the graph of the line, making linear equations a powerful tool for predicting and understanding real-world scenarios.
A linear equation in the slope-intercept form, for example, looks like this:
- \( y = mx + b \), where \( m \) is the slope of the line and \( b \) is the y-intercept (the point where the line crosses the y-axis).
By identifying the slope and y-intercept, you can quickly sketch the graph of the line, making linear equations a powerful tool for predicting and understanding real-world scenarios.
Coordinate Geometry
Coordinate geometry, also known as analytic geometry, lets us observe and analyze geometric properties using coordinates on a graph. Each point on a graph is defined by its coordinates, often written as \((x, y)\), which specify its position relative to the x-axis and y-axis.
This system allows us to find the distance between two points, the slope of a line, and other important geometric measures directly from numerical coordinates.
Key Concepts:
This system allows us to find the distance between two points, the slope of a line, and other important geometric measures directly from numerical coordinates.
Key Concepts:
- Distance Formula: The formula \( \sqrt{(x_2-x_1)^2 + (y_2-y_1)^2} \) calculates how far one point is from another in the coordinate plane.
- Slope Formula: The formula \( m = \frac{y_2-y_1}{x_2-x_1} \) finds the direction and steepness between two points.
Point-Slope Form
The point-slope form is a linear equation format that highlights the slope of a line and a specific point on the line. It is especially useful when you know the slope and a single point but not the y-intercept. The formula for point-slope form is:
Steps to Use Point-Slope Form:
- \( y - y_1 = m(x - x_1) \), where \( m \) is the slope, and \((x_1, y_1)\) is an exact point on the line.
Steps to Use Point-Slope Form:
- Identify a point on the line \((x_1, y_1)\).
- Use the slope \( m \) of the line.
- Plug the values into \( y - y_1 = m(x - x_1) \) to form the equation.