Linear Equations in Two Variables
Site: | Saylor Academy |
Course: | GKT101: General Knowledge for Teachers – Math |
Book: | Linear Equations in Two Variables |
Printed by: | Guest user |
Date: | Tuesday, July 1, 2025, 4:17 AM |
Description
While the solution of a linear equation in one variable is one value of x, the solution of an equation in two variables is an ordered pair of values, x and y. When these solutions are plotted on the coordinate plane, they form a line (hence the term "linear" equation). Watch this lecture series, which explains how to find and graph the solutions of a linear equation in two variables. Complete the interactive exercises.
Two-variable linear equations intro
Source: Khan Academy, https://www.khanacademy.org/math/algebra/x2f8bb11595b61c86:linear-equations-graphs#x2f8bb11595b61c86:two-variable-linear-equations-intro
This work is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 3.0 License.
Solutions to 2-variable equations
Worked example: solutions to 2-variable equations
Completing solutions to 2-variable equations
Solutions to 2-variable equations - Questions
1. Which ordered pair is a solution of the equation?
\(y=7 x-3\)
Choose 1 answer:
A. Only \((1, 4) \)
B. Only \((-1, -4) \)
C. Both \((1, 4) \) and \((-1, -4) \)
D. Neither
2. Which ordered pair is a solution of the equation?
\(y=-2 x+5\)
A. Only \((2, -9) \)
B. Only \((-2, 9) \)
C. Both \((2, -9) \) and \((-2, 9) \)
D. Neither
3. Which ordered pair is a solution of the equation?
\(2 x+4 y=6 x-y\)
A. Only \((4, 5) \)
B. Only \((5, 4) \)
C. Both \((4, 5) \) and \((5, 4) \)
D. Neither
4. Which ordered pair is a solution of the equation?
\(-x-4 y=-10\)
A. Only \((3, 2) \)
B. Only \((-3, 3) \)
C. Both \((3, 2) \) and \((-3, 3) \)
D. Neither
Answers
1. A. Only \((1, 4) \)
To check whether an ordered pair \((a,b)\) is a solution of an equation, substitute these values into the equation and determine if the resulting equality is true or false.
To check whether \((1,4)\) is a solution of the equation, let's substitute \(x=1\) and \(y=4\) into the equation:
\(\begin{aligned}
&y=7 x-3 \\
&4=7 \cdot 1-3 \\
&4=7-3 \\
&4=4
\end{aligned}\)
Since \(4=4\), we obtained a true statement, so \((1, 4)\) is indeed a solution of the equation.
To check whether \((-1, -4)\) is a solution of the equation, let's substitute \(x=-1\) and \(y=-4\) into the equation:
\(\begin{aligned}
y &=7 x-3 \\
-4 &=7 \cdot(-1)-3 \\
-4 &=-7-3 \\
-4 &=-10
\end{aligned}\)
Since \(-4 \neq-10\), we obtained a false statement, so \((-1, -4)\) is not a solution of the equation.
Only \((1, 4)\) a solution of the equation.
2. B. Only \((-2, 9) \)
To check whether an ordered pair \((a, b) \) is a solution of an equation, substitute these values into the equation and determine if the resulting equality is true or false.
To check whether \( (2, -9\), let's substitute \(x=2\) and \(y=-9\) into the equation:
\(\begin{aligned}
y &=-2 x+5 \\
-9 &=-2 \cdot 2+5 \\
-9 &=-4+5 \\
-9 &=1
\end{aligned}\)
Since \( -9 \neq 1\), we obtained a false statement, so \((2, -9) \) is not a solution of the equation.
To check whether \( (-2, 9)\), let's substitute \(x=-2\) and \(y=9\) into the equation:
\(\begin{aligned}
&y=-2 x+5 \\
&9=-2 \cdot(-2)+5 \\
&9=4+5 \\
&9=9
\end{aligned}\)
Since \(9 = 9\), we obtained a true statement, so \( (-2, 9 )\) is indeed a solution of the equation.
Only \( (-2, 9 )\) is a solution of the equation.
3. B. Only \((5, 4) \)
To check whether an ordered pair \((a,b)\) is a solution of an equation, substitute these values into the equation and determine if the resulting equality is true or false.
To check whether\((4, 5) \) is a solution of the equation, let's substitute \(x=4\) and \(y=5\) into the equation:
\(\begin{aligned}
2 x+4 y &=6 x-y \\
2 \cdot 4+4 \cdot 5 &=6 \cdot 4-5 \\
8+20 &=24-5 \\
28 &=19
\end{aligned}\)
Since \(28 \neq 19\), we obtained a false statement, so \((4, 5)\) is not a solution of the equation.
To check whether\((5, 4) \) is a solution of the equation, let's substitute \(x=5\) and \(y=4\) into the equation:
\(\begin{aligned}
2 x+4 y &=6 x-y \\
2 \cdot 5+4 \cdot 4 &=6 \cdot 5-4 \\
10+16 &=30-4 \\
26 &=26
\end{aligned}\)
Since \(26 = 26\), we obtained a true statement, so \((5, 4)\) is indeed a solution of the equation.
Only \((5, 4)\)is a solution of the equation.
4. D. Neither
To check whether an ordered pair \((a, b\) is a solution of an equation, substitute these values into the equation and determine if the resulting equality is true or false.
To check whether \((3, 2) \) is a solution of the equation, let's substitute \(x= 3\) and \(y = 2\) into the equation:
\(\begin{aligned}
-x-4 y &=-10 \\
-3-4 \cdot 2 &=-10 \\
-3-8 &=-10 \\
-11 &=-10
\end{aligned}\)
Since \( -11 \neq-10\), we obtained a false statement, so \((3, 2) \) is not a solution of the equation.
To check whether \((-3, 3) \) is a solution of the equation, let's substitute \(x= -3\) and \(y = 3\) into the equation:
\( \begin{aligned}
-x-4 y &=-10 \\
-(-3)-4 \cdot 3 &=-10 \\
3-12 &=-10 \\
-9 &=-10
\end{aligned}\)
Since \(-9 \neq-10\), we obtained a false statement, so \((-3, 3) \) is not a solution of the equation.
Neither of the ordered pairs is a solution of the equation.
Complete solutions to 2-variable equations - Questions
1. \(y-4=-2(x+3)\)
Complete the missing value in the solution to the equation.
\( (-3, \text { ____ }) \)
2.\(-4 x-y=24\)
Complete the missing value in the solution to the equation.
\( (\text { ____ }, 8) \)
3. \(-3 x+7 y=5 x+2 y\)
Complete the missing value in the solution to the equation.
\( (-5, \text { ____ }) \)
4. \(2 x+3 y=12\)
Complete the missing value in the solution to the equation.
\( (\text { ____ }, 8) \)
Answers
1. \((-3,4)\)
To find the \(y\)-value that corresponds to \(x=3\), let's substitute this \(x\)-value in the equation.
\(\begin{aligned}
&y-4=-2(x+3) \\
&y-4=-2(-3+3) \\
&y-4=-2 \cdot 0 \\
&y-4=0 \\
&y=4
\end{aligned}\)
Therefore \((-3,4)\) is a solution of the equation.
2. \( (-8, 8)\)
To find the \(x\)-value that corresponds to \(y=8\), let's substitute this \(y\)-value in the equation.
\(\begin{aligned}
-4 x-y &=24 \\
-4 x-8 &=24 \\
-32 &=4 x \\
-8 &=x
\end{aligned}\)
Therefore \( (-8, 8)\) is a solution of the equation.
3. \((-5, -8)\)
To find the \(y\)-value that corresponds to \(x = -5\), let's substitute this xxx-value in the equation.
\(\begin{aligned}
-3 x+7 y &=5 x+2 y \\
-3 \cdot(-5)+7 y &=5 \cdot(-5)+2 y \\
15+7 y &=-25+2 y \\
5 y &=-40 \\
y &=-8
\end{aligned}\)
Therefore \((-5, -8)\) is a solution of the equation.
4. \( (-6, 8) \)
To find the \(x\)-value that corresponds to \(y = 8\), let's substitute this yyy-value in the equation.
\(\begin{aligned}
2 x+3 y &=12 \\
2 x+3 \cdot 8 &=12 \\
2 x+24 &=12 \\
2 x &=-12 \\
x &=-6
\end{aligned}\)
Therefore \((-6, 8) \) is a solution of the equation.