Mathematics
Grade 8
15 min
Evaluate a linear function
Evaluate a linear function
Tutorial Preview
1
Introduction & Learning Objectives
Learning Objectives
Define what a linear function is and identify its components.
Understand and correctly use function notation, such as f(x).
Substitute a given numerical value for the input variable in a linear function's equation.
Apply the order of operations (PEMDAS) to accurately calculate the output of a linear function.
Interpret the meaning of an evaluated linear function in real-world contexts.
Distinguish between the input and output of a linear function.
Ever wonder how a store calculates your total bill based on the number of items you buy? 🛒 Or how scientists predict temperature changes? 🌡️
In this lesson, you'll learn how to 'evaluate' linear functions, which means finding the output of a function when you know its input. This skill is f...
2
Key Concepts & Vocabulary
TermDefinitionExample
FunctionA special relationship where every input has exactly one output.The relationship between the number of hours worked and the money earned (for a fixed hourly wage) is a function.
Linear FunctionA function whose graph is a straight line and can be written in the form y = mx + b or f(x) = mx + b.y = 2x + 3 is a linear function. Its graph is a straight line.
Input (Domain)The value you put *into* the function, usually represented by 'x'. It's the independent variable.In the function f(x) = 2x + 3, if you choose x = 5, then 5 is the input.
Output (Range)The value that comes *out* of the function after applying the rule, usually represented by 'y' or 'f(x)'. It's the dependent variable.In the function f(x) = 2x + 3, if the in...
3
Core Formulas
Standard Form of a Linear Function
$$y = mx + b$$
This is a common way to write a linear function, where 'm' is the slope (rate of change) and 'b' is the y-intercept (starting value). To evaluate, substitute the given 'x' value into the equation and simplify.
Function Notation for a Linear Function
$$f(x) = mx + b$$
This notation is equivalent to y = mx + b. f(x) represents the output value for a given input x. To evaluate f(a), substitute 'a' for every 'x' in the function's rule.
Process of Evaluation
To evaluate $f(a)$, replace every instance of $x$ in the function's rule with the specific value $a$, then simplify the expression using the order of operations (PEMDAS/BODMAS).
This rule guides the step-by-st...
5 more steps in this tutorial
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Challenging
For the function f(x) = 3x - 7, for what value of x is f(x) = 11?
A.26
B.4
C.6
D.1.33
Challenging
Function A is f(x) = 2x + 5 and Function B is g(x) = -x + 14. For which input value 'x' is f(x) equal to g(x)?
A.9
B.5
C.3
D.19
Challenging
A point (k, 20) lies on the graph of the linear function f(x) = 4x + 8. What is the value of k?
A.88
B.3
C.7
D.12
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