CAIE P3 2021 November — Question 4 5 marks

Exam BoardCAIE
ModuleP3 (Pure Mathematics 3)
Year2021
SessionNovember
Marks5
PaperDownload PDF ↗
Mark schemeDownload PDF ↗
TopicPartial Fractions
TypeImproper fraction with linear factors – division then partial fractions
DifficultyModerate -0.5 This is a straightforward improper fraction requiring polynomial division followed by standard partial fraction decomposition. While it involves an extra step compared to proper fractions, the algebraic manipulation is routine and mechanical with no conceptual challenges beyond applying the standard algorithm.
Spec1.02y Partial fractions: decompose rational functions

4 Express \(\frac { 4 x ^ { 2 } - 13 x + 13 } { ( 2 x - 1 ) ( x - 3 ) }\) in partial fractions.

Question 4:
AnswerMarks Guidance
AnswerMark Guidance
State or imply the form \(A + \frac{B}{2x-1} + \frac{C}{x-3}\)B1 \(\frac{Dx+E}{2x-1} + \frac{F}{x-3}\) and \(\frac{P}{2x-1} + \frac{Qx+R}{x-3}\) are also valid
Use a correct method for finding a constantM1
Obtain one of \(A = 2\), \(B = -3\) and \(C = 2\)A1 Allow maximum M1A1 for one or more 'correct' values after B0
Obtain a second valueA1
Obtain the third valueA1
Alternative method for Question 4:
AnswerMarks Guidance
AnswerMark Guidance
Divide numerator by denominatorM1
Obtain \(2\left[+\frac{Px+Q}{(2x-1)(x-3)}\right]\)A1 \(\left[2 + \frac{x+7}{(2x-1)(x-3)}\right]\)
State or imply the form \(\frac{D}{2x-1} + \frac{E}{x-3}\)B1
Obtain one of \(D = -3\) and \(E = 2\)A1
Obtain a second valueA1
Total: 5 marks
## Question 4:

| Answer | Mark | Guidance |
|--------|------|----------|
| State or imply the form $A + \frac{B}{2x-1} + \frac{C}{x-3}$ | **B1** | $\frac{Dx+E}{2x-1} + \frac{F}{x-3}$ and $\frac{P}{2x-1} + \frac{Qx+R}{x-3}$ are also valid |
| Use a correct method for finding a constant | **M1** | |
| Obtain one of $A = 2$, $B = -3$ and $C = 2$ | **A1** | Allow maximum **M1A1** for one or more 'correct' values after **B0** |
| Obtain a second value | **A1** | |
| Obtain the third value | **A1** | |

**Alternative method for Question 4:**

| Answer | Mark | Guidance |
|--------|------|----------|
| Divide numerator by denominator | **M1** | |
| Obtain $2\left[+\frac{Px+Q}{(2x-1)(x-3)}\right]$ | **A1** | $\left[2 + \frac{x+7}{(2x-1)(x-3)}\right]$ |
| State or imply the form $\frac{D}{2x-1} + \frac{E}{x-3}$ | **B1** | |
| Obtain one of $D = -3$ and $E = 2$ | **A1** | |
| Obtain a second value | **A1** | |

**Total: 5 marks**

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4 Express $\frac { 4 x ^ { 2 } - 13 x + 13 } { ( 2 x - 1 ) ( x - 3 ) }$ in partial fractions.\\

\hfill \mbox{\textit{CAIE P3 2021 Q4 [5]}}