Other multiples
In the Warm-up, we looked at mapping diagrams for functions of the form \(f(x)=3x+b\).
We also used certain conventions when we drew those mapping diagrams, both to allow for fair comparison and to restrict the number of things we varied between the diagrams:
- the numberlines are a fixed distance apart
- the scales on the two numberlines are equal (so \(\quantity{1}{cm}\) represents the same difference on each numberline)
- the centre arrow is horizontal
- the arrow start points are a fixed distance apart
What would the mapping diagrams of other functions of the form \(f(x)=ax+b\) look like?
Using the same conventions, draw mapping diagrams for these functions. You can choose what your centre input value will be and what scale you will use.
- \(f(x)=2x+1\)
- \(f(x)=\frac{1}{2}x-1\)
- \(f(x)=x\)
- \(f(x)=-x\)
- \(f(x)=-2x+2\)
- another function of your choosing
What do you notice?
You can download blank mapping diagrams or small blank mapping diagrams for this.
Extending the arrows
We could extend the arrows into straight lines, as shown here for \(f(x)=3x\), with just one arrow extended so far:
What patterns do you notice when you extend the arrows for different linear functions?
What does this tell you about the nature of linear functions?
You can explore this further using the first of the interactivities.
A chance to reflect
How does this mapping diagram representation of a linear function \(f(x)=ax+b\) relate to the representation as the graph of \(y=ax+b\)?
Which features of the function are clearer in one representation rather than the other?
- How are the features in one representation related to features in the other?
