1MA0 Higher March 2013 Paper 2 Q14

14 \(A = 4bc\)

\(A = 100\)
\(b = 2\)

(a) Work out the value of \(c\). (2)

\[m = \sqrt{\frac{k + 1}{4}}\]

(b) Make \(k\) the subject of the formula. (3)

Working	Answer	Mark	Notes
\(100 = 4 \times 2 \times c\)	12.5	2	M1 for correct substitution into formula A1 for 12.5 oe

Mark scheme (b)

Working	Answer	Mark	Notes
\(m^2 = \dfrac{k + 1}{4}\) \(4m^2 = k + 1\) \(k = 4m^2 - 1\) or \(2m = \sqrt{(k + 1)}\) \(4m^2 = k + 1\) \(k = 4m^2 - 1\)	\(k = 4m^2 - 1\)	3	M1 for correct method to clear fraction or remove square root sign M1 (dep) for a fully correct method to both clear fraction and remove square root sign A1 for \(k = 4m^2 - 1\) or \(k = (2m + 1)(2m - 1)\)