Modulus Functions (DP IB Analysis & Approaches (AA)): Revision Note

Dan Finlay

Last updated

Modulus Functions & Graphs

What is the modulus function?

  • The modulus function is defined by f left parenthesis x right parenthesis equals open vertical bar x close vertical bar

    • open vertical bar x close vertical bar equals square root of x squared end root

    • Equivalently it can be defined open vertical bar x close vertical bar equals open curly brackets table row x cell x greater or equal than 0 end cell row cell negative x end cell cell x less than 0 end cell end table close

  • Its domain is the set of all real values

  • Its range is the set of all real non-negative values

  • The modulus function gives the distance between 0 and x

    • This is also called the absolute value of x

What are the key features of the modulus graph: y = |x|?

  • The graph has a y-intercept at (0, 0)

  • The graph has one root at (0, 0)

  • The graph has a vertex at (0, 0)

  • The graph is symmetrical about the y-axis

  • At the origin

    • The function is continuous

    • The function is not differentiable

2-4-2-ib-aa-hl-modulus-function

What are the key features of the modulus graph: y = a|x + p| + q?

  • Every modulus graph which is formed by linear transformations can be written in this form using key features of the modulus function

    • open vertical bar a x close vertical bar equals open vertical bar a close vertical bar open vertical bar x close vertical bar

      • For example: open vertical bar 2 x plus 1 close vertical bar equals 2 open vertical bar x plus 1 half close vertical bar

    • open vertical bar p minus x close vertical bar equals open vertical bar x minus p close vertical bar

      • For example: open vertical bar 4 minus x close vertical bar equals open vertical bar x minus 4 close vertical bar

  • The graph has a y-intercept when x = 0

  • The graph can have 0, 1 or 2 roots

    • If a and q have the same sign then there will be 0 roots

    • If q = 0 then there will be 1 root at (-p, 0)

    • If a and q have different signs then there will be 2 roots at open parentheses negative p plus-or-minus q over a comma 0 close parentheses

  • The graph has a vertex at (-p, q)

  • The graph is symmetrical about the line x = -p

  • The value of a determines the shape and the steepness of the graph

    • If a is positive the graph looks like logical or

    • If a is negative the graph looks like logical and

    • The larger the value of |a| the steeper the lines

  • At the vertex

    • The function is continuous

    • The function is not differentiable

👀 You've read 1 of your 5 free revision notes this week
An illustration of students holding their exam resultsUnlock more revision notes. It's free!

By signing up you agree to our Terms and Privacy Policy.

Already have an account? Log in

Did this page help you?

Dan Finlay

Author: Dan Finlay

Expertise: Maths Subject Lead

Dan graduated from the University of Oxford with a First class degree in mathematics. As well as teaching maths for over 8 years, Dan has marked a range of exams for Edexcel, tutored students and taught A Level Accounting. Dan has a keen interest in statistics and probability and their real-life applications.

Download notes on Modulus Functions