Practice Input-Output View in Math

Use these practice problems to test your method after reviewing the concept explanation and worked examples.

Quick Recap

The input-output view of a function treats it as a black box: put in a value (input), get out a uniquely determined value (output), without worrying about the internal mechanism.

Like a vending machine: put in selection (input), get out snack (output).

Showing a random 20 of 50 problems.

Example 1

easy
Think of f(x)=3x−7 as a machine. Describe the sequence of operations applied to input x, then evaluate f(5) and find the input that gives output 14.

Example 2

challenge
Machines: f(x)=2x and g(x)=x+3. Find an input x with f(g(x))=g(f(x)).

Example 3

medium
Two machines: f doubles, g adds 3. Find g(f(2)).

Example 4

easy
Must the inputs of a function be numbers?

Example 5

challenge
Given f(x)=2x+3, find a function g so that f(g(x))=x.

Example 6

medium
For f(x)=4x−9, find the input that gives output −1.

Example 7

easy
Is f the same as f(3)?

Example 8

easy
Does f(x) mean f multiplied by x?

Example 9

medium
If f(x)=1x−2, which input is NOT allowed, and why (input-output view)?

Example 10

easy
For f(x)=x+4, fill in the table: f(0),f(1),f(−2).

Example 11

medium
If f(3)=7 and f(5)=7, is f a function? Is it one-to-one?

Example 12

easy
A function maps each student to their birth year. Is birth year the input or the output?

Example 13

easy
In f(7)=12, which number is the input and which is the output?

Example 14

easy
If g squares its input, what is g(4)?

Example 15

medium
For f(x)=3−2x, find f(a+1).

Example 16

medium
If f(x)=2x+1 and g(x)=x−3, find f(g(5)).

Example 17

hard
If f(x)=3x+1, find the inverse machine that recovers x from f(x).

Example 18

medium
If f(x)=ax+b and f(2)=5, f(4)=11, find a and b.

Example 19

medium
For f(x)=3x−2, find the input that produces output 10.

Example 20

easy
Can two different inputs share the same output in a function?