Chapter 9: Problem 2
Solve each linear system of equations. In addition, for each system, graph the two lines corresponding to the two equations in a single coordinate system and use your graph to explain your solution. $$ \begin{array}{r} 2 x+3 y=6 \\ x-4 y=-4 \end{array} $$
Short Answer
Expert verified
The solution to the system is \( x = \frac{12}{11} \) and \( y = \frac{14}{11} \), where the lines intersect.
Step by step solution
01
Identify the Equations
The given system of equations is:1. \( 2x + 3y = 6 \)2. \( x - 4y = -4 \). These are the two equations that we need to solve simultaneously.
02
Solve Equation 2 for x
Take the second equation: \( x - 4y = -4 \).Rearrange it to express \( x \) in terms of \( y \):\[ x = 4y - 4 \].
03
Substitute Expression for x in Equation 1
Replace \( x \) in the first equation with \( 4y - 4 \):\[ 2(4y - 4) + 3y = 6 \].This leads to the equation \( 8y - 8 + 3y = 6 \).
04
Simplify and Solve for y
Combine like terms:\[ 11y - 8 = 6 \].Add 8 to both sides:\[ 11y = 14 \].Divide both sides by 11:\[ y = \frac{14}{11} \].
05
Substitute y Back into Expression for x
Now use \( y = \frac{14}{11} \) to find \( x \):\[ x = 4 \left( \frac{14}{11} \right) - 4 \].Calculate:\[ x = \frac{56}{11} - \frac{44}{11} = \frac{12}{11} \].
06
State the Solution
The solution to the system is \( x = \frac{12}{11} \) and \( y = \frac{14}{11} \). This means the lines intersect at this point, which is the single solution to the system.
07
Graph the Equations
Graph the equations by converting them to slope-intercept form:1. For equation 1: \( y = -\frac{2}{3}x + 2 \).2. For equation 2: \( y = \frac{1}{4}x + 1 \).Plot both lines on the same coordinate plane. The point where they intersect is \( \left( \frac{12}{11}, \frac{14}{11} \right) \), confirming the solution.
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
graphing linear equations
When graphing linear equations, you're drawing a line that represents all the solutions to the equation. Each linear equation can be graphed on a coordinate system. Here’s how you do it:
- First, find the y-intercept, which is where the line crosses the y-axis. In equation form, it’s the constant term in the slope-intercept form, or the value of y when x is 0.
- Next, use the slope, which is the steepness of the line. The slope is the coefficient of x in slope-intercept form, represented as 'm' in the equation \( y = mx + b \).
- Finally, plot the y-intercept on the graph. Use the slope to find the next point by moving up or down, and left or right. A positive slope means the line rises as it moves right, and a negative slope means it falls.
solving simultaneously
Solving systems of equations simultaneously means finding a common solution for both equations where their graphs intersect. There are different ways to solve them, but solving them algebraically is quite efficient.
In the given exercise:
In the given exercise:
- You first rearrange one equation to express one variable in terms of the other.
- Next, substitute this expression into the other equation. This substitution allows you to have one equation with a single variable, making it possible to solve for that variable.
- Once you find one variable, substitute it back into the rearranged equation to find the second variable.
slope-intercept form
The slope-intercept form is a way of writing the equation of a line. It is a simplified form that makes it easy to graph the equation and understand the line's properties.
The general form of the slope-intercept equation is \( y = mx + b \), where:
Understanding this form is essential because it helps you quickly graph the line and appreciate its slope and intercept visually.
The general form of the slope-intercept equation is \( y = mx + b \), where:
- 'm' represents the slope. It shows the rate at which y changes for a change in x. It's calculated as \( \frac{\text{rise}}{\text{run}} \).
- 'b' is the y-intercept. This is where the line crosses the y-axis, or the value of y when x equals 0.
Understanding this form is essential because it helps you quickly graph the line and appreciate its slope and intercept visually.