Chapter 2: Problem 73
Exer. 73-74: Graph the lines on the same coordinate plane, and estimate the coordinates of the points of Intersection. Identify the polygon determined by the lines. $$2 x-y=-1 ; \quad x+2 y=-2 ; \quad 3 x+y=11$$
Short Answer
Expert verified
The polygon formed is a triangle with vertices at approximately \((-\frac{4}{5},\frac{2}{5})\), \((\frac{16}{5}, -\frac{13}{5})\), and \((2,5)\).
Step by step solution
01
Rearrange Equations into Slope-Intercept Form
First, we need to transform each of the given equations into the slope-intercept form, which is \( y = mx + b \).\1. For the first equation, \(2x - y = -1\): \[ y = 2x + 1 \]2. For the second equation, \(x + 2y = -2\): \[ y = -\frac{1}{2}x - 1 \]3. For the third equation, \(3x + y = 11\): \[ y = -3x + 11 \]
02
Graph the Lines
Using the slope-intercept form of each equation, plot the lines on a coordinate plane. Use the y-intercept and the slope to draw each line:
1. Line 1: Starts at (0,1) and rises 2 units for every 1 unit it runs to the right.
2. Line 2: Starts at (0,-1) and falls 1 unit for every 2 units it runs to the right.
3. Line 3: Starts at (0,11) and falls 3 units for every 1 unit it runs to the right.
03
Estimate Points of Intersection
Observe where the lines intersect each other on the graph:1. Intersection of Line 1 and Line 2: Solve \(2x + 1 = -\frac{1}{2}x - 1\), resulting in \(x = -\frac{4}{5}\), and \(y = \frac{2}{5}\).2. Intersection of Line 2 and Line 3: Solve \(-\frac{1}{2}x - 1 = -3x + 11\), resulting in \(x = \frac{16}{5}\), and \(y = -\frac{13}{5}\).3. Intersection of Line 1 and Line 3: Solve \(2x + 1 = -3x + 11\), resulting in \(x = 2\), and \(y = 5\).
04
Identify the Polygon
Now that you have found the intersection points, check how they connect:- The points of intersection are \((-\frac{4}{5},\frac{2}{5})\), \((\frac{16}{5}, -\frac{13}{5})\), and \((2,5)\).- Connect these points to form the polygon.- Since there are three sides formed by three intersecting lines, the resulting polygon is a triangle.
Unlock Step-by-Step Solutions & Ace Your Exams!
-
Full Textbook Solutions
Get detailed explanations and key concepts
-
Unlimited Al creation
Al flashcards, explanations, exams and more...
-
Ads-free access
To over 500 millions flashcards
-
Money-back guarantee
We refund you if you fail your exam.
Over 30 million students worldwide already upgrade their learning with 91Ó°ÊÓ!
Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Slope-Intercept Form
The slope-intercept form is a way of writing a linear equation, which allows you to easily see the slope and the y-intercept of the line. This form is presented as \( y = mx + b \), where:
- \( m \) represents the slope of the line. It shows how steep the line is, indicating the rise (change in y) over the run (change in x).
- \( b \) is the y-intercept, which is the point where the line crosses the y-axis.
- For \( 2x - y = -1 \), we have \( y = 2x + 1 \).
- For \( x + 2y = -2 \), the form turns into \( y = -\frac{1}{2}x - 1 \).
- Finally, \( 3x + y = 11 \) becomes \( y = -3x + 11 \).
Graphing Lines
With equations in slope-intercept form, graphing becomes straightforward. The y-intercept \( b \) tells us where to start on the y-axis. The slope \( m \) tells how many units to move up or down for each unit we move right.
- For the equation \( y = 2x + 1 \), start at \( (0,1) \) and move 2 units up for 1 unit to the right.
- \( y = -\frac{1}{2}x - 1 \) indicates starting at \( (0,-1) \) and moving 1 unit down for every 2 units to the right.
- Lastly, \( y = -3x + 11 \) starts at \( (0,11) \) and moves down 3 units for every 1 unit to the right.
Coordinate Plane
The coordinate plane is a two-dimensional space where we can plot points, lines, and shapes. It's divided into four quadrants by the x-axis (horizontal) and y-axis (vertical).
- Each point is represented by a pair of values \((x, y)\).
- The x-coordinate tells us how far the point is to the right or left of the y-axis.
- The y-coordinate tells us how far up or down the point is from the x-axis.
Intersection Points
Intersection points are where two lines meet on a graph. They represent the solutions to a system of equations, showing where the conditions described by each equation are true simultaneously. Let's explore how we solve for these points:
- Select two equations and set them equal to find their intersection.
- For example, solving \( 2x + 1 = -\frac{1}{2}x - 1 \) gives \( x = -\frac{4}{5} \) and \( y = \frac{2}{5} \), marking one intersection point.
- Continue with the other pairs: \(-\frac{1}{2}x - 1 = -3x + 11\) yields \( x = \frac{16}{5} \), \( y = -\frac{13}{5} \) and so on.
- Intersections from \( 2x + 1 = -3x + 11 \) result in \( x = 2 \), \( y = 5 \).