4MA0 Higher January 2014 Paper 3R Q16
16 Make \(r\) the subject of the formula \(A = 4r^2 - \pi r^2\) where \(r\) is positive.
(3)
| Scheme | Marks |
|---|---|
| \(A = (4 - \pi)r^2\) or \(\dfrac{A}{r^2} = 4 - \pi\) | M1 |
| \(r^2 = \dfrac{A}{4 - \pi}\) | M1 |
| \(\sqrt{\dfrac{A}{4 - \pi}}\) | A1 |
| (3) | |
| (3 marks) |
Notes
M1: for isolating \(r^2\)
A1: Also accept \(\pm\sqrt{\dfrac{A}{4 - \pi}}\)