What Is a Function?
Grade 8 · Math · Functions · New Jersey, USA
Lesson Summary
Learn what makes a relationship a function and how to tell if a relation qualifies.
Explanation
A function is a rule that assigns exactly one output to each input. Think of it like a vending machine: you press one button and get one specific item. If you could press the same button and sometimes get chips and sometimes get candy, that would not be a function. You can check whether a graph represents a function using the vertical line test—if any vertical line touches the graph in more than one spot, it is not a function.
Practice Questions
Q1: Is the set {(1, 3), (2, 5), (1, 7)} a function? Why or why not?
Answer: No, it is not a function because the input 1 is paired with two different outputs (3 and 7).
Q2: Explain the vertical line test.
Answer: Draw vertical lines across the graph. If any vertical line hits the graph at more than one point, the graph does not represent a function.
Q3: Is y = 3x + 2 a function?
Answer: Yes. For every value of x there is exactly one value of y, so it meets the definition of a function.
People Also Ask
What is What Is a Function? in Grade 8 Math?+
What Is a Function? is a lesson in the Functions chapter of Grade 8 Math. It is part of the New Jersey, USA school curriculum and covers key concepts that students need to understand at this level.
What grade level covers What Is a Function??+
What Is a Function? is taught in Grade 8 as part of the Math curriculum in New Jersey, USA.
How can I help my child with Functions in Math?+
Start with the lesson summary and explanation on this page. Practice the questions provided, then use TutorTom for personalized, step-by-step help with Functions topics.