Warm-up

In this resource, we will explore linear functions and how they can be represented. This is interesting in its own right, and also gives us a tool to think about an important idea in calculus. We will take this further in Mapping a derivative.

Here are mapping diagrams representing functions of the form \(f(x)=ax+b\) for \(x\in\mathbb{R}\).

(In these diagrams, the left-hand numberline is the input and the right-hand one is the output, for example in Diagram 1, \(f(1)=3\).)

figure 1 is two parallel numberlines, left one centred on zero, right one centred on zero, both going up in steps of one, five arrows from left line to right line, from 0 to 0, from one half to 1.5, from 1 to 3, from minus one half to minus 1.5, from minus 1 to minus 3
Diagram 1
looks identical to figure 1 except now numberlines are renumbered: left one is centred at 2, right one is centred at 6, still going up in steps of one
Diagram 2
looks identical to figure 1 except now numberlines are renumbered: left one is centred at 2, right one is centred at 6, both lines now go up in steps of 0.01
Diagram 3
looks identical to figure 1 except now numberlines are renumbered: left one is centred at 2, right one is centred at 7, still going up in steps of one
Diagram 4
looks identical to figure 1 except now numberlines are renumbered: left one is centred at 1, right one is centred at 1, still going up in steps of one
Diagram 5
looks identical to figure 1 except now numberlines are renumbered: left one is centred at 1, right one is centred at 2, both lines now go up in steps of 0.1
Diagram 6
  • What do you notice about these diagrams and the functions they represent? (You might find it helpful to work out some or all of the functions first.)

  • What features do the diagrams and functions have in common? What are the differences between them?