Higher November 2018 Paper 1 Q21
21.
(a) Janesh wants to draw the graph of \(y = f(x)\) and the graph of \(y = -f(x)\).
Janesh says,
Janesh says,
‘To draw \(y = -f(x)\) I must reflect the graph of \(y = f(x)\) in the \(y\)-axis because the \(y\)-coordinates all change sign.’
Is Janesh correct?Yes ☐ No ☐
Explain how you decide. [1](b) Yasmin wants to draw the graph of \(y = f(x)\) and the graph of \(y = -f(x)\)
when \(f(x) = \dfrac{1}{x}\).
Yasmin draws both of her graphs on this diagram.
when \(f(x) = \dfrac{1}{x}\).
Yasmin draws both of her graphs on this diagram.
| Scheme | Marks | Comments |
|---|---|---|
| No implied or indicated with valid explanation e.g. ‘(All the \(y\)-coordinates change sign so) it is a reflection in the \(x\)- axis’ | E1 |
| Scheme | Marks | Comments |
|---|---|---|
| Valid criticism e.g. ‘The graphs are not labelled so you cannot tell which is which’ or ‘None of the branches should cross the \(x\)-axis’ | E1 | Allow e.g. ‘There is no scale so she might have drawn something like \(\dfrac{2}{x}\) and \(-\dfrac{2}{x}\).’ |
| (2) |