Higher June 2017 Paper 1 Q13
13 The table shows a set of values for \(x\) and \(y\).
| \(x\) | 1 | 2 | 3 | 4 |
|---|---|---|---|---|
| \(y\) | 9 | \(2\dfrac{1}{4}\) | 1 | \(\dfrac{9}{16}\) |
\(y\) is inversely proportional to the square of \(x\).
(a) Find an equation for \(y\) in terms of \(x\). (2)
(b) Find the positive value of \(x\) when \(y = 16\) (2)
| Answer | Mark | Notes |
|---|---|---|
| \(y = \dfrac{9}{x^2}\) | M1 | begins to work with \(y = \dfrac{k}{x^2}\) oe e.g. subs of a pair of numbers into \(y = \dfrac{k}{x^2}\) or states \(k = 9\) |
| A1 | for \(y = \dfrac{9}{x^2}\) Accept \(y = 9x^{-2}\) |
| Answer | Mark | Notes |
|---|---|---|
| \(\dfrac{3}{4}\) | M1 | ft (dep on previous M1) subs \(y = 16\) into proportional formula of the form \(y = \dfrac{k}{x^2}\) oe |
| A1 | oe |