Mathematics
Grade 11
15 min
Multiply functions
Multiply functions
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1
Introduction & Learning Objectives
Learning Objectives
Correctly use the notation for the product of two functions.
Algebraically determine the new function created by multiplying two functions, such as polynomials or rational functions.
Determine the domain of a product of two functions by finding the intersection of their individual domains.
Evaluate the product of two functions at a specific input value.
Distinguish between multiplying functions, (f * g)(x), and composing functions, f(g(x)).
Simplify the resulting product function by combining like terms or factoring.
Imagine a company's revenue is a function of time, and its profit margin is another. How could you create a new function to model their total profit over time? 📈
This tutorial will guide you through the process of multiplying functions...
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Key Concepts & Vocabulary
TermDefinitionExample
FunctionA relation between a set of inputs (the domain) and a set of possible outputs (the range) where each input is related to exactly one output.f(x) = 3x + 2 is a linear function. For an input of x=5, the unique output is f(5) = 3(5) + 2 = 17.
Domain of a FunctionThe complete set of all possible input values (x-values) for which the function is defined.For the function g(x) = 1/(x-4), the domain is all real numbers except x=4, because at x=4, the denominator would be zero. We write this as {x | x ≠4}.
Product of FunctionsA new function created by multiplying the output values of two or more existing functions for each input value in their common domain.If f(x) = x and g(x) = x + 1, their product is (f * g)(x) = f(x) * g(x) = x(x + 1) = x² + x.
Polynomial Functio...
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Core Formulas
The Product Rule for Functions
(f \cdot g)(x) = f(x) \cdot g(x)
This is the fundamental definition for multiplying two functions, f(x) and g(x). The notation (f * g)(x) means to create a new function by multiplying the expressions for f(x) and g(x).
The Domain of a Product Function
Domain(f \cdot g) = Domain(f) \cap Domain(g)
The domain of the product function (f * g) is the intersection of the domains of the individual functions f and g. An input 'x' must be valid for both f(x) and g(x) to be valid for their product.
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Challenging
Let f(x) = 1/x, g(x) = 1/(x-2), and h(x) = 1/(x+2). What is the domain of the product function (f â‹… g â‹… h)(x)?
A.{x | x ≠0}
B.{x | x ≠0, x ≠2, x ≠-2}
C.{x | x ≠2, x ≠-2}
D.All real numbers
Challenging
Let f(x) = (x² - 9)/(x + 1) and g(x) = (x² - x - 2)/(x - 3). Find the domain of (f ⋅ g)(x).
A.{x | x ≠-1 and x ≠3}
B.{x | x ≠-1, x ≠3, and x ≠-3}
C.{x | x ≠-2 and x ≠-3}
D.All real numbers
Challenging
Let f(x) = x² - 4x - 5 and g(x) = x² - 1. Find the set of all zeros for the function (f ⋅ g)(x).
A.{-1, 1}
B.{-1, 5}
C.{1, 5}
D.{-1, 1, 5}
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