June 2016 Paper 1 Q10
10 \(\sqrt[4]{x} = 2 \ \) and \(\ y^{-2} = 25\)
\(x \gt 0\) and \(y \lt 0\)
Work out the value of \(\dfrac{x}{y}\) [4 marks]
| Answer | Mark | Comments |
|---|---|---|
| \(x = 2^4\) or \(x = 16\) | B1 | |
| \(\dfrac{1}{y^2} = 25\) or \(y^2 = \dfrac{1}{25}\) or \(25y^2 = 1\) or \(y = \sqrt{\dfrac{1}{25}}\) or \(y = \left(\dfrac{1}{25}\right)^{\frac{1}{2}}\) | M1 | |
| (\(y\) =) \(-\dfrac{1}{5}\) or \(\pm\dfrac{1}{5}\) or \(\dfrac{1}{5}\) | A1 | oe eg 0.2 |
| \(-80\) | A1 |
Additional guidance
Condone \(4^2\) for the 1st M1
80 seen is likely to be 3 marks ... but check
(\(y\) =) \(-\dfrac{1}{5}\) or \(\pm\dfrac{1}{5}\) or \(\dfrac{1}{5}\) with no incorrect working seen implies M1 A1
(\(y\) =) \(-\dfrac{1}{5}\) or \(\pm\dfrac{1}{5}\) or \(\dfrac{1}{5}\) from clearly incorrect working scores M0 A0