Higher November 2020 Paper 2R Q17
17 Given that \(n \gt 0\)
make \(n\) the subject of the formula \(\;y = \dfrac{n^2 + d}{n^2}\)
(4)
| Scheme | Marks |
|---|---|
| \(yn^2 = n^2 + d\) or \(y = 1 + \dfrac{d}{n^2}\) | M1 |
| \(yn^2 - n^2 = d\) or \(-d = n^2 - yn^2\) or \(y - 1 = \dfrac{d}{n^2}\) | M1 |
| \(n^2(y - 1) = d\) or \(-d = (1 - y)n^2\) | M1 |
| \(n = \sqrt{\dfrac{d}{y - 1}}\) | A1 |
| (4) | |
| (4 marks) |
Notes
M1: for factorising \(n^2\) from a suitable expression.
or \(n^2 = \dfrac{d}{y - 1}\)
A1: Accept \(n = \sqrt{\dfrac{-d}{1 - y}}\)
Penalise \(\pm\sqrt{\phantom{x}}\)