Mathematics
Grade 8
15 min
Complete a table for a two-variable relationship
Complete a table for a two-variable relationship
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1
Introduction & Learning Objectives
Learning Objectives
Identify independent and dependent variables in a two-variable relationship.
Substitute given input values into an algebraic equation.
Calculate corresponding output values for a given equation using the order of operations.
Organize input and output values into a clear table.
Recognize patterns in tables generated from linear equations.
Use a table to represent a two-variable relationship described by a word problem.
Ever wonder how a recipe tells you exactly how much flour for a certain number of cookies? 🍪 That's a two-variable relationship in action!
In this lesson, you'll learn how to complete tables that show how two variables are related. This skill is fundamental for understanding linear functions and graphing, which are key to solving...
2
Key Concepts & Vocabulary
TermDefinitionExample
VariableA symbol (usually a letter) that represents a quantity that can change or take on different values.In the equation $y = 2x + 1$, $x$ and $y$ are variables.
Two-Variable RelationshipA connection between two variables where the value of one variable depends on the value of the other.The total cost of apples ($C$) depends on the number of apples ($n$) you buy.
EquationA mathematical statement that shows two expressions are equal, often used to describe a two-variable relationship.$y = 3x - 5$ is an equation describing a relationship between $x$ and $y$.
Input (Independent Variable)The variable whose value is chosen or given, which then determines the value of the other variable. It is typically represented by $x$.In $y = 2x + 1$, $x$ is the input variable.
Outpu...
3
Core Formulas
General Form of a Linear Equation
$y = mx + b$
This is the standard form for a linear relationship between two variables, $x$ and $y$, where $m$ is the slope (rate of change) and $b$ is the y-intercept (starting value). Many two-variable relationships you'll encounter in Grade 8 will follow this pattern.
The Substitution Principle
If $y = \text{expression involving } x$, then for a specific input value $x_0$, $y_0 = \text{expression involving } x_0$.
To find the output ($y$) for any given input ($x$), replace every instance of $x$ in the equation with the specific input value. Then, calculate the result following the order of operations to find the corresponding output value.
5 more steps in this tutorial
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Challenging
A candle is 12 inches tall and burns at a rate of 0.5 inches per hour. Let 'h' be the height of the candle and 't' be the time in hours. Which table correctly represents the candle's height over time?
A.| t | h |
|---|---|
| 0 | 0.5 |
| 2 | 1.5 |
| 4 | 2.5 |
B.| t | h |
|---|---|
| 0 | 12 |
| 1 | 12.5|
| 2 | 13 |
C.| t | h |
|---|---|
| 1 | 11.5|
| 2 | 11 |
| 3 | 10.5|
D.| t | h |
|---|---|
| 0 | 12 |
| 2 | 11 |
| 4 | 10 |
Challenging
A student created a table for the equation y = -2x + 5. Which ordered pair (x, y) in their table is incorrect?
| x | y |
|---|---|
| -1| 7 |
| 0 | 5 |
| 2 | 1 |
| 3 | -2|
A.(-1, 7)
B.(0, 5)
C.(3, -2)
D.(2, 1)
Challenging
The ordered pair (k, 10) is a solution to the equation y = 3x - 5. What is the value of k?
A.25
B.5
C.10
D.3
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