Mathematics
Grade 12
15 min
Find values of inverse functions from tables
Find values of inverse functions from tables
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1
Introduction & Learning Objectives
Learning Objectives
Define the relationship between a function and its inverse by swapping input and output values.
Evaluate an inverse function, f⁻¹(y), for a specific value using a table of values for f(x).
Solve composite functions involving inverses, such as f(g⁻¹(x)), using data from two separate tables.
Determine if a function is invertible by analyzing its table of values for one-to-one correspondence.
Apply the formula for the derivative of an inverse function to find (f⁻¹)'(a) using a table that includes values for f(x) and f'(x).
Interpret the meaning of an inverse function's value within a real-world context presented in a table.
How does a temperature conversion app instantly switch from Celsius to Fahrenheit? 🌡️ It uses the same principle as inver...
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Key Concepts & Vocabulary
TermDefinitionExample
FunctionA mathematical rule that assigns exactly one output value for each unique input value.If f(x) = x², the input x=3 has exactly one output, f(3)=9.
Inverse Function (f⁻¹)A function that reverses the action of another function. If a function f takes an input 'a' to an output 'b', its inverse f⁻¹ takes 'b' back to 'a'.If f(x) = 2x, then f(3) = 6. The inverse function is f⁻¹(x) = x/2, and f⁻¹(6) = 3.
One-to-One FunctionA function where every output value is associated with exactly one input value. A function must be one-to-one to have an inverse.f(x) = x³ is one-to-one. However, f(x) = x² is not, because the output 4 corresponds to two inputs, x=2 and x=-2.
DomainThe complete set of possible input values (typically x-values)...
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Core Formulas
The Fundamental Inverse Relationship
If f(a) = b, then f⁻¹(b) = a
This is the core principle. To find the value of an inverse function for a given input, you treat that input as an *output* of the original function and find the corresponding *input*.
Composition of Inverses
f(f⁻¹(x)) = x and f⁻¹(f(x)) = x
When a function and its inverse are composed, they cancel each other out, returning the original input value, provided the value is in the appropriate domain.
Derivative of an Inverse Function
(f⁻¹)'(a) = \frac{1}{f'(f⁻¹(a))}
This crucial calculus formula allows you to find the derivative of an inverse function at a point 'a' by using the derivative of the original function, f', evaluated at the point f⁻¹(a).
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Easy
The function f(x) is one-to-one. Use the table below to find the value of f⁻¹(5).
A.0
B.-2
C.4
D.1
Easy
Based on the table of values below, can the function g(x) be considered one-to-one on the domain provided?
A.Yes, because every input has exactly one output.
B.Yes, because the x-values are all unique.
C.No, because the output value 4 is repeated for two different inputs.
D.No, because the function is not continuous.
Easy
The function f(x) is one-to-one. A common mistake when finding f⁻¹(3) is to look at x=3 in the table. What is the result of this common error, and what is the correct value of f⁻¹(3)?
A.Error: 4; Correct: 1
B.Error: 1; Correct: 4
C.Error: 5; Correct: -2
D.Error: 4; Correct: 5
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