| Exam Board | AQA |
|---|---|
| Module | C4 (Core Mathematics 4) |
| Year | 2016 |
| Session | June |
| Marks | 8 |
| Paper | Download PDF ↗ |
| Mark scheme | Download PDF ↗ |
| Topic | Polynomial Division & Manipulation |
| Type | Integration Using Polynomial Division |
| Difficulty | Standard +0.3 Part (a) is a standard algebraic division exercise requiring polynomial long division or comparison of coefficients—routine C4 content. Part (b) applies the result to integrate term-by-term, yielding a logarithmic answer in the specified form. Both parts follow textbook procedures with no novel insight required, making this slightly easier than average for A-level. |
| Spec | 1.02k Simplify rational expressions: factorising, cancelling, algebraic division1.02y Partial fractions: decompose rational functions1.08d Evaluate definite integrals: between limits1.08j Integration using partial fractions |
| Answer | Marks | Guidance |
|---|---|---|
| \(\frac{3 + 13x - 6x^2}{2x - 3} = Ax + B + \frac{C}{2x - 3}\) | M1 | e.g. using \(x = \frac{3}{2}\) in an attempt to find \(C\) or forming simultaneous equations and attempt to solve. |
| Answer | Marks | Guidance |
|---|---|---|
| Correct above equation and attempt to find one of \(A\), \(B\) or \(C\) or an attempt at long division | ||
| \(A = -3\) | A1 | |
| \(B = 2\) | A1 | |
| \(C = 9\) | A1 | Total: 4 |
| Answer | Marks |
|---|---|
| Alternative method of division \(\frac{3+13x-6x^2}{2x-3} = \frac{-3x(2x-3)-9x+13x+3}{2x-3} = -3x + \frac{4x+3}{2x-3}\) | M1 for \(-3x + \cdots\), |
| Answer | Marks | Guidance |
|---|---|---|
| \(\int\frac{3+13x-6x^2}{2x-3}dx = \int(-3x + 2 + \frac{9}{2x-3})dx\) | M1 | |
| \(= px^2 + qx + r\ln(2x - 3)\) | ||
| \(= -\frac{3}{2}x^2 + 2x + \frac{9}{2}\ln(2x - 3)\) | A1ft | \(\frac{4}{3}x^2 + Bx + \frac{5}{2}\ln(2x - 3)\) |
| Answer | Marks | Guidance |
|---|---|---|
| \(= \left[-\frac{3}{2}\cdot 6^2 + 2.6 + \frac{9}{2}\ln(12 - 3)\right]\) | m1 | Correct substitution of limits for their \(p, q\) and \(r\). |
| Answer | Marks | Guidance |
|---|---|---|
| \(= -\frac{69}{2} + \frac{9}{2}\ln3\) | A1 | Total: 4 |
| Answer | Marks | Guidance |
|---|---|---|
| Total | 8 |
## Part (a)
$\frac{3 + 13x - 6x^2}{2x - 3} = Ax + B + \frac{C}{2x - 3}$ | M1 | e.g. using $x = \frac{3}{2}$ in an attempt to find $C$ or forming simultaneous equations and attempt to solve.
$3 + 13x - 6x^2 = Ax(2x - 3) + B(2x - 3) + C$
Correct above equation and attempt to find one of $A$, $B$ or $C$ or an attempt at long division | |
$A = -3$ | A1 |
$B = 2$ | A1 |
$C = 9$ | A1 | Total: 4
If long division is used award M1 once $-3x + \cdots$ has been obtained but only award the A marks once the values are clearly identified or it is written in the required form of $Ax + B + \frac{C}{2x - 3}$
Alternative method of division $\frac{3+13x-6x^2}{2x-3} = \frac{-3x(2x-3)-9x+13x+3}{2x-3} = -3x + \frac{4x+3}{2x-3}$ | M1 for $-3x + \cdots$,
For the A marks, $A$, $B$ and $C$ must be clearly identified or seen in the required form of $Ax + B + \frac{C}{2x-3}$
NMS scores B2 for one correct value, B3 for 2 correct values and B4 for all three correct values
## Part (b)
$\int\frac{3+13x-6x^2}{2x-3}dx = \int(-3x + 2 + \frac{9}{2x-3})dx$ | M1 |
$= px^2 + qx + r\ln(2x - 3)$ | |
$= -\frac{3}{2}x^2 + 2x + \frac{9}{2}\ln(2x - 3)$ | A1ft | $\frac{4}{3}x^2 + Bx + \frac{5}{2}\ln(2x - 3)$
Correct use of $F(6) - F(3)$
$= \left[-\frac{3}{2}\cdot 6^2 + 2.6 + \frac{9}{2}\ln(12 - 3)\right]$ | m1 | Correct substitution of limits for their $p, q$ and $r$.
$- \left[-\frac{3}{2}\cdot 3^2 + 2.3 + \frac{9}{2}\ln(6 - 3)\right]$
$= -\frac{69}{2} + \frac{9}{2}\ln3$ | A1 | Total: 4 | OE
The M1 A1ft and m1 can be earned even if left in terms of $A, B$ and $C$ or if 'invented' value(s) for $A, B$ and $C$ are used.
Condone missing brackets from the $\ln(2x - 3)$ term for the M1 mark but only award the A1ft mark if they have clearly recovered; PI by sight of $\ln9$ or $\ln3$ after using the limits or a correct final answer.
Treat a decimal answer (should be–29.55 ...) after a correct exact form as ISW but award A0 if an exact answer is not seen.
Total | | 8
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\begin{enumerate}[label=(\alph*)]
\item Express $\frac{3 + 13x - 6x^2}{2x - 3}$ in the form $Ax + B + \frac{C}{2x - 3}$.
[4 marks]
\item Show that $\int_3^6 \frac{3 + 13x - 6x^2}{2x - 3} \, dx = p + q \ln 3$, where $p$ and $q$ are rational numbers.
[4 marks]
\end{enumerate}
\hfill \mbox{\textit{AQA C4 2016 Q3 [8]}}