Mathematics
Grade 8
15 min
Evaluate a nonlinear function
Evaluate a nonlinear function
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1
Introduction & Learning Objectives
Learning Objectives
Define what a nonlinear function is and distinguish it from a linear function.
Identify the input (independent variable) and output (dependent variable) in a given function.
Accurately substitute numerical values for the independent variable into a nonlinear function's equation.
Apply the order of operations (PEMDAS/BODMAS) correctly to simplify expressions within nonlinear functions.
Calculate the output (function value) for a given input in various nonlinear functions.
Express the evaluation of a nonlinear function using standard function notation.
Ever wonder how rollercoasters are designed or how a ball flies through the air? 🎢 These movements aren't straight lines; they follow curves described by special mathematical rules!
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2
Key Concepts & Vocabulary
TermDefinitionExample
FunctionA rule that assigns exactly one output value to each input value. Think of it like a machine: you put something in, and it gives you exactly one thing out.The function $f(x) = 2x + 1$ takes an input $x$ and gives an output $2x+1$. For $x=3$, the output is $2(3)+1=7$.
Nonlinear FunctionA function whose graph is not a straight line. Its equation often involves variables raised to powers other than 1 (like $x^2$, $x^3$) or variables in the denominator.$f(x) = x^2$ is a nonlinear function because its graph is a curve (a parabola).
Input (Independent Variable)The value that is substituted into the function. It's the 'cause' or the value you choose. It's typically represented by $x$ or another letter like $t$ for time.In $f(x) = x^2 + 5$, if we...
3
Core Formulas
Function Notation
$f(x) = \text{expression involving } x$
This notation represents a function where $x$ is the input (independent variable) and $f(x)$ is the output (dependent variable). Other letters like $g(t)$ or $h(z)$ can also be used.
Evaluating a Function
To evaluate $f(x)$ at $x=a$, substitute $a$ for every $x$ in the expression: $f(a) = \text{expression with } a \text{ substituted for } x$.
This rule tells you exactly how to find the output for a given input. Replace all instances of the variable with the specific number and then simplify using the order of operations.
Order of Operations (PEMDAS)
$P \rightarrow E \rightarrow MD \rightarrow AS$
Always follow this order when simplifying expressions: Parentheses first, then Exponents, then Multiplication and D...
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Challenging
Given f(x) = x² + 5 and g(x) = 2x³, what is the value of the expression f(4) + g(-1)?
A.23
B.19
C.21
D.14
Challenging
For the function f(x) = x² + 2x, which input value for x results in an output of 15?
A.2
B.-5
C.5
D.-3
Challenging
Evaluate the function f(x) = 8x² - 6x for x = -1/2.
A.-1
B.-5
C.1
D.5
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