Main problem

Can you arrange functions in these \(2 \times 2\) tables?

Once you have completed a function square, can you find other functions which also fit?

We have provided some functions on printed cards and you can either work with the equations of the functions or with their graphs. (Please note that we haven’t excluded any input values for \(x\) on the cards because one of the properties to be considered is whether these functions are defined for all real values of \(x.\))

Graph passes through \((0,0)\)

Graph has rotational symmetry about \((0,0)\)

\[f(x)= \cdots\]

Graph passes through \((0,0)\)

Graph does not have rotational symmetry about \((0,0)\)

\[f(x)= \cdots\]

Graph does not pass through \((0,0)\)

Graph has rotational symmetry about \((0,0)\)

\[f(x)= \cdots\]

Graph does not pass through \((0,0)\)

Graph does not have rotational symmetry about \((0,0)\)

\[f(x)= \cdots\]

Function is defined for all real \(x\)

Different values of \(x\) always give different values of \(f(x)\)

\[f(x)= \cdots\]

Function is defined for all real \(x\)

Different values of \(x\) may give the same value of \(f(x)\)

\[f(x)= \cdots\]

Function is not defined for some real \(x\)

Different values of \(x\) always give different values of \(f(x)\)

\[f(x)= \cdots\]

Function is not defined for some real \(x\)

Different values of \(x\) may give the same value of \(f(x)\)

\[f(x)= \cdots\]

Could you try to form a function square for other properties of functions?

Take a look at some of the functions you have used and at any other functions you have thought about. What is the same and what is different about these functions?

  • the graph of the function is straight, i.e. the graph has constant gradient

  • the graph of the function passes through the origin, i.e. \(f(0)=0\)

  • different input values (values of \(x\)) all give different output values (values of \(f(x)\))

  • the graph has asymptotes (lines which the graph of the function gets arbitrarily close to)

  • the \(y\)-axis is a line of symmetry (the function is even)

  • rotational symmetry about the origin (the function is odd)

  • the function could be defined for all real values of \(x\), i.e. all real values of \(x\) are suitable as inputs

From a completed function square, can you work out which properties might have been used?

Are there properties that can never be combined to make a function square?