4MA0 Foundation June 2012 Paper 1 Q14
14
\[A = 2x^2 + kx\](a) \(x = -3\)
\(k = 4\)
Work out the value of \(A\). (2)
\(k = 4\)
Work out the value of \(A\). (2)
(b) \(A = 38\)
\(x = 4\)
Work out the value of \(k\). (3)
\(x = 4\)
Work out the value of \(k\). (3)
| Scheme | Marks |
|---|---|
| \(2 \times (-3)^2 + 4 \times (-3)\) or \(2 \times -3^2 + 4 \times -3\) or \(2 \times 9 - 4 \times 3\) or \(18 - 12\) or \(18 + -12\) | M1 |
| 6 | A1 |
| (2) |
Notes
M1: for substitution or for correct evaluation of either 18 or −12
A1: cao
| Scheme | Marks |
|---|---|
\(38 = 2 \times 4^2 + 4k\) or \((k) = \dfrac{A - 2x^2}{x}\) oe | M1 |
| \(4k = 38 - 32\) or \(4k = 6\) | M1 |
| 1.5 oe | A1 |
| (3) | |
| (Total 5 marks) |
Notes
M1: for correct substitution or rearrangement
SC M2 for \(\dfrac{38 - 32}{4}\)
M1: for correct rearrangement of correct substitution