Chapter 3: Problem 22
Solve each system graphically. Be sure to check your solution. If a system has an infinite number of solutions, use set-builder notation to write the solution set. If \(a\) system has no solution, state this. $$ \begin{aligned} 4 x-y &=9 \\ x-3 y &=16 \end{aligned} $$
Short Answer
Expert verified
The solution is the point (1, -5).
Step by step solution
01
- Rewrite equations in slope-intercept form
To graph the equations, convert them to the slope-intercept form, which is \(y = mx + b\). For the first equation, rewrite it as follows: \(4x - y = 9\)\[-y = -4x + 9\]y = 4x - 9For the second equation, rewrite it as follows: \(x - 3y = 16\)x - 16 = 3y\[y = \frac{1}{3}x - \frac{16}{3} \].
02
- Graph the equations
Graph the equations on the same coordinate system. The first equation is \(y = 4x - 9\), which has a slope of 4 and a y-intercept of -9. The second equation is \(y = \frac{1}{3}x - \frac{16}{3}\), which has a slope of \( \frac{1}{3}\) and a y-intercept of \(-\frac{16}{3}\).
03
- Find the intersection point
Determine where the lines intersect by solving the system of equations. Set the equations equal to each other:\[4x - 9 = \frac{1}{3}x - \frac{16}{3}\]Multiply both sides by 3 to clear the fraction:\[12x - 27 = x - 16\]Collect like terms:\[11x = 11\]Divide by 11:\[x = 1\]Substitute \(x = 1\) back into one of the original equations to find \(y\):\[4(1) - y = 9\]\[4 - y = 9\]\[y = -5\].
04
- Verify the solution
Verify the solution by substituting \(x = 1\) and \(y = -5\) into both original equations.For \(4x - y = 9\): \[4(1) - (-5) = 9\]\[4 + 5 = 9\], which is true.For \(x - 3y = 16\)\[1 - 3(-5) = 16\]\[1 + 15 = 16\], which is true.
05
- State the solution
Since both equations are satisfied by \(x = 1\) and \(y = -5\), the solution to the system is the point (1, -5).
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
slope-intercept form
To solve a system of equations graphically, it is helpful to start by converting each equation into slope-intercept form. This form is represented as: \(y = mx + b\), where \(m\) is the slope, and \(b\) is the y-intercept. Starting with the slope-intercept form helps you easily draw each line on a coordinate plane. For the given equations, we convert them as follows:
- \bm{Equation 1:} \(4x - y = 9\)\- y = -4x + 9\y = 4x - 9\
- \bm{Equation 2:} \(x - 3y = 16\)\x = 3y + 16\y = \frac{1}{3}x - \frac{16}{3}\
graphing linear equations
Once your equations are in slope-intercept form, you can graph them on a coordinate plane. This step involves:
- \bm{Identifying the y-intercept (b):} The point where the line crosses the y-axis.
- \bm{Using the slope (m):} To determine the rise over run from the y-intercept. For the line \(y = 4x - 9\), the slope is 4, which means for each step of 1 unit right, the line moves 4 units up.
- \bm{For the second line \(y = \frac{1}{3}x - \frac{16}{3}\):} The slope is \( \frac{1}{3}\), meaning the line moves up 1 unit for every 3 units to the right.
intersection point
The intersection point of the graph's lines represents the solution to the system of equations. To find this point graphically:
- \bm{Set equations equal:} \(4x - 9 = \frac{1}{3}x - \frac{16}{3}\)
- \bm{Clear fractions:} Multiply both sides by 3 \( \rightarrow 12x - 27 = x - 16 \)
- \bm{Solve for x:} Combine like terms \( \rightarrow 11x = 11 \)
- \bm{Find x:} \( x = 1 \)
- \bm{Substitute x back:} Into either original equation to find y \(4(1) - 9 = -5 \)
- \bm{Solution:} The intersection point and solution is (1, -5)
solution verification
Always verify your solution by substituting back into the original equations. This ensures the solution satisfies both equations.
For our solution \(x = 1\) and \(y = -5\):
For our solution \(x = 1\) and \(y = -5\):
- \bm{Equation 1:} \(4(1) - (-5) = 9 \)\4 + 5 = 9\
- \bm{Equation 2:} \(1 - 3(-5) = 16 \)\1 + 15 = 16\