Chapter 4: Problem 18
Solve each system of linear equations by graphing. See Examples 3 through \(6 .\) \(\left\\{\begin{array}{l}2 x+y=1 \\ 3 x+y=0\end{array}\right.\)
Short Answer
Expert verified
The solution to the system is \((-1, 3)\).
Step by step solution
01
Convert Equations to Slope-Intercept Form
To graph the equations, we need them in slope-intercept form, which is \(y = mx + b\). For the first equation \(2x + y = 1\), we rearrange to get \(y = -2x + 1\). For the second equation \(3x + y = 0\), we rearrange to get \(y = -3x\).
02
Graph the First Equation
Plot the line for the equation \(y = -2x + 1\). Start by plotting the y-intercept \((0, 1)\). From there, use the slope \(-2\), meaning go down 2 units and right 1 unit from the y-intercept to mark another point \( (1, -1) \). Draw a line through these points.
03
Graph the Second Equation
Plot the line for the equation \(y = -3x\). Start by plotting the y-intercept \((0, 0)\). From there, use the slope \(-3\), meaning go down 3 units and right 1 unit to mark another point \((1, -3)\). Draw a line through these points.
04
Identify the Point of Intersection
Find where the two lines intersect - this point is the solution to the system of equations. The lines intersect at \((-1, 3)\).
05
Verify the Solution
Substitute \((-1, 3)\) into the original equations to verify it works for both: - For \(2x + y = 1\): substitute to get \(2(-1) + 3 = 1\), which is true. - For \(3x + y = 0\): substitute to get \(3(-1) + 3 = 0\), which is also true.
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Graphing Linear Equations
Graphing linear equations is a visual way to display relationships between variables. It involves plotting equations on a coordinate grid so that their solutions can be identified easily. Each equation corresponds to a straight line on this graph. To begin, you need to express each equation in slope-intercept form, which helps in easily identifying both the slope and the y-intercept. The y-intercept is the point where the line crosses the y-axis.
- Select two key points - the y-intercept and another point determined by the slope.
- Plot these points on the graph and draw a straight line through them.
Slope-Intercept Form
The slope-intercept form of a linear equation is written as: \[ y = mx + b \]where \( m \) represents the slope and \( b \) represents the y-intercept. This form is beneficial for quickly drawing graphs, as it provides a straightforward way to locate both the starting point and direction of the line.
- The slope \( m \) describes the steepness of the line. It tells you how many units to move up or down for each unit you move to the right.
- The y-intercept \( b \) is where the line crosses the y-axis.
Point of Intersection
The point of intersection of two lines on a graph represents the solution to a system of linear equations. This is the precise point where both equations have the same values for \( x \) and \( y \).
- To find it graphically, carefully plot both equations on the same set of axes.
- Look for the point where the two lines intersect, which can often be seen as a clear crossing point.
Verifying Solutions
Once you have a proposed solution from the graph, it is essential to verify it by plugging the point of intersection back into the original equations.
- Substitute the \( x \) and \( y \) values into each equation separately.
- Ensure that each equation holds true with these substituted values.
- For the first equation: \[ 2(-1) + 3 = 1 \]which simplifies accurately.
- For the second equation: \[ 3(-1) + 3 = 0 \]which confirms the correctness as well.