Cambridge A Level Mathematics - Further 9231 — 2023 May/June Paper 1 · Variant 2

This document has 20 pages. Any blank pages are indicated. [Turn over Cambridge International AS & A Level DC (PQ) 311427/1 © UCLES 2023 * 5 5 7 2 6 8 0 2 0 5 * FURTHER MATHEMATICS 9231/12 Paper 1 Further Pure Mathematics 1 May/June 2023 2 hours You must answer on the question paper. You will need: List of formulae (MF19) INSTRUCTIONS ● Answer all questions. ● Use a black or dark blue pen. You may use an HB pencil for any diagrams or graphs. ● Write your name, centre number and candidate number in the boxes at the top of the page. ● Write your answer to each question in the space provided. ● Do not use an erasable pen or correction fluid. ● Do not write on any bar codes. ● If additional space is needed, you should use the lined page at the end of this booklet; the question number or numbers must be clearly shown. ● You should use a calculator where appropriate. ● You must show all necessary working clearly; no marks will be given for unsupported answers from a calculator. ● Give non-exact numerical answers correct to 3 significant figures, or 1 decimal place for angles in degrees, unless a different level of accuracy is specified in the question. INFORMATION ● The total mark for this paper is 75. ● The number of marks for each question or part question is shown in brackets [ ].

2 9231/12/M/J/23 © UCLES 2023 BLANK PAGE

3 9231/12/M/J/23 © UCLES 2023 [Turn over 1 Let A 3 1 0 1 = e o. (a) Prove by mathematical induction that, for all positive integers n, A 2 2 3 3 1 0 2 n n n # = - e o. [5] … … … … … … … … … … … … … … … … … … … (b) Find, in terms of n, the inverse of An. [2] … … … …

4 9231/12/M/J/23 © UCLES 2023 2 The cubic equation x x x 4 6 1 0 3 2 + + + = has roots a, b, c. (a) Find the value of 2 2 2 a b c + + . [2] … … … … … … … … … … (b) Use standard results from the list of formulae (MF19) to show that ( ) ( ) ( ) ( ) r r r n n an b r n 2 1 2 2 2 a b c + + + + + = + + = ` j / , where a and b are constants to be determined. [6] … … … … … … … … … … … …

5 9231/12/M/J/23 © UCLES 2023 [Turn over … … … … … … … … … … … … … … … … … … … … … … … … … … … …

6 9231/12/M/J/23 © UCLES 2023 3 (a) Use the method of differences to find ( )( ) kr kr k 1 1 1 r n 1 + - + =/ in terms of n and k , where k is a positive constant. [4] … … … … … … … … … … … … … … … … … … … … … … … … … …

7 9231/12/M/J/23 © UCLES 2023 [Turn over (b) Deduce the value of ( )( ) kr kr k 1 1 1 r 1 + - + 3 =/ . [1] … … … … … (c) Find also ( )( ) kr kr k 1 1 1 r n n2 + - + =/ in terms of n and k. [2] … … … … … … … … … … … … … … … … … … …

8 9231/12/M/J/23 © UCLES 2023 4 The matrix M is given by a a b M 2 2 = c e o, where a, b, c are real constants and b 0 ! . (a) Show that M does not represent a rotation about the origin. [2] … … … … … (b) Find the equations of the invariant lines, through the origin, of the transformation in the x – y plane represented by M. [5] … … … … … … … … … … … … … … … … … … …

9 9231/12/M/J/23 © UCLES 2023 [Turn over … … … … … … … … It is given that M represents the sequence of two transformations in the x – y plane given by an enlargement, centre the origin, scale factor 5 followed by a shear, x-axis fixed, with (0, 1) mapped to (5, 1). (c) Find M. [3] … … … … … … … … … … (d) The triangle DEF in the x – y plane is transformed by M onto triangle PQR. Given that the area of triangle DEF is 12 cm2, find the area of triangle PQR. [2] … … … … …

10 9231/12/M/J/23 © UCLES 2023 5 The curve C has polar equation r 1 1 2 2 i = + , for r 0 G G i . (a) Sketch C and state the polar coordinates of the point of C furthest from the pole. [3] … (b) Find the area of the region enclosed by C, the initial line, and the half-line r i = . [4] … … … … … … … … … … … … … …

11 9231/12/M/J/23 © UCLES 2023 [Turn over (c) Show that, at the point of C furthest from the initial line, cot 1 1 0 i i i + - = e o and verify that this equation has a root between 1.1 and 1.2. [5] … … … … … … … … … … … … … … … … … … … … … … … … …

12 9231/12/M/J/23 © UCLES 2023 6 The curve C has equation y x x x 2 2 15 2 = - + - . (a) Find the equations of the asymptotes of C. [3] … … … … … … … … … … … … (b) Show that C has no stationary points. [3] … … … … … … … … … … … … …

13 9231/12/M/J/23 © UCLES 2023 [Turn over (c) Sketch C, stating the coordinates of the intersections with the axes. [3] … (d) Sketch the curve with equation y x x x 2 15 2 2 = - - - . [2]

14 9231/12/M/J/23 © UCLES 2023 (e) Find the set of values of x for which x x x 2 2 4 30 15 2 1 - + - . [4] … … … … … … … … … … … … … … … … … … … … … … … … … …

15 9231/12/M/J/23 © UCLES 2023 [Turn over BLANK PAGE

16 9231/12/M/J/23 © UCLES 2023 7 The plane 1 P has equation ( ) ( ) r j k i j k i j k 4 3 m n = - - + - + + + - . (a) Obtain an equation of 1 P in the form px qy rz d + + = . [4] … … … … … … … … … … … … (b) The plane 2 P has equation ( ) r. i j k 5 3 5 4 - + + = . Find a vector equation of the line of intersection of 1 P and 2 P . [4] … … … … … … … … … … … …

17 9231/12/M/J/23 © UCLES 2023 The line l passes through the point A with position vector ( ) a a a i j k 7 + + - and is parallel to ( ) b b b i j k 1- + + , where a and b are positive constants. (c) Given that the perpendicular distance from A to 1 P is 2, find the value of a. [2] … … … … … … … … … … (d) Given that the obtuse angle between l and 1 P is 4 3 r, find the exact value of b. [4] … … … … … … … … … … … … … … …

18 9231/12/M/J/23 © UCLES 2023 Additional page If you use the following page to complete the answer to any question, the question number must be clearly shown. … … … … … … … … … … … … … … … … … … … … … … … … … …

19 9231/12/M/J/23 © UCLES 2023 BLANK PAGE

20 9231/12/M/J/23 © UCLES 2023 Permission to reproduce items where third-party owned material protected by copyright is included has been sought and cleared where possible. Every reasonable effort has been made by the publisher (UCLES) to trace copyright holders, but if any items requiring clearance have unwittingly been included, the publisher will be pleased to make amends at the earliest possible opportunity. To avoid the issue of disclosure of answer-related information to candidates, all copyright acknowledgements are reproduced online in the Cambridge Assessment International Education Copyright Acknowledgements Booklet. This is produced for each series of examinations and is freely available to download at www.cambridgeinternational.org after the live examination series. Cambridge Assessment International Education is part of Cambridge Assessment. Cambridge Assessment is the brand name of the University of Cambridge Local Examinations Syndicate (UCLES), which is a department of the University of Cambridge. BLANK PAGE

This document consists of 16 printed pages. © UCLES 2023 [Turn over Cambridge International AS & A Level FURTHER MATHEMATICS 9231/12 Paper 1 Further Pure Mathematics 12 May/June 2023 MARK SCHEME Maximum Mark: 75 Published This mark scheme is published as an aid to teachers and candidates, to indicate the requirements of the examination. It shows the basis on which Examiners were instructed to award marks. It does not indicate the details of the discussions that took place at an Examiners’ meeting before marking began, which would have considered the acceptability of alternative answers. Mark schemes should be read in conjunction with the question paper and the Principal Examiner Report for Teachers. Cambridge International will not enter into discussions about these mark schemes. Cambridge International is publishing the mark schemes for the May/June 2023 series for most Cambridge IGCSE, Cambridge International A and AS Level and Cambridge Pre-U components, and some Cambridge O Level components.

9231/12 Cambridge International AS & A Level – Mark Scheme PUBLISHED May/June 2023 © UCLES 2023 Page 2 of 16 Generic Marking Principles These general marking principles must be applied by all examiners when marking candidate answers. They should be applied alongside the specific content of the mark scheme or generic level descriptors for a question. Each question paper and mark scheme will also comply with these marking principles. GENERIC MARKING PRINCIPLE 1: Marks must be awarded in line with:  the specific content of the mark scheme or the generic level descriptors for the question  the specific skills defined in the mark scheme or in the generic level descriptors for the question  the standard of response required by a candidate as exemplified by the standardisation scripts. GENERIC MARKING PRINCIPLE 2: Marks awarded are always whole marks (not half marks, or other fractions). GENERIC MARKING PRINCIPLE 3: Marks must be awarded positively:  marks are awarded for correct/valid answers, as defined in the mark scheme. However, credit is given for valid answers which go beyond the scope of the syllabus and mark scheme, referring to your Team Leader as appropriate  marks are awarded when candidates clearly demonstrate what they know and can do  marks are not deducted for errors  marks are not deducted for omissions  answers should only be judged on the quality of spelling, punctuation and grammar when these features are specifically assessed by the question as indicated by the mark scheme. The meaning, however, should be unambiguous. GENERIC MARKING PRINCIPLE 4: Rules must be applied consistently, e.g. in situations where candidates have not followed instructions or in the application of generic level descriptors. GENERIC MARKING PRINCIPLE 5: Marks should be awarded using the full range of marks defined in the mark scheme for the question (however; the use of the full mark range may be limited according to the quality of the candidate responses seen). GENERIC MARKING PRINCIPLE 6: Marks awarded are based solely on the requirements as defined in the mark scheme. Marks should not be awarded with grade thresholds or grade descriptors in mind.

9231/12 Cambridge International AS & A Level – Mark Scheme PUBLISHED May/June 2023 © UCLES 2023 Page 3 of 16 Mathematics Specific Marking Principles 1 Unless a particular method has been specified in the question, full marks may be awarded for any correct method. However, if a calculation is required then no marks will be awarded for a scale drawing. 2 Unless specified in the question, answers may be given as fractions, decimals or in standard form. Ignore superfluous zeros, provided that the degree of accuracy is not affected. 3 Allow alternative conventions for notation if used consistently throughout the paper, e.g. commas being used as decimal points. 4 Unless otherwise indicated, marks once gained cannot subsequently be lost, e.g. wrong working following a correct form of answer is ignored (isw). 5 Where a candidate has misread a number in the question and used that value consistently throughout, provided that number does not alter the difficulty or the method required, award all marks earned and deduct just 1 mark for the misread. 6 Recovery within working is allowed, e.g. a notation error in the working where the following line of working makes the candidate’s intent clear.

9231/12 Cambridge International AS & A Level – Mark Scheme PUBLISHED May/June 2023 © UCLES 2023 Page 4 of 16 Mark Scheme Notes The following notes are intended to aid interpretation of mark schemes in general, but individual mark schemes may include marks awarded for specific reasons outside the scope of these notes. Types of mark M Method mark, awarded for a valid method applied to the problem. Method marks are not lost for numerical errors, algebraic slips or errors in units. However, it is not usually sufficient for a candidate just to indicate an intention of using some method or just to quote a formula; the formula or idea must be applied to the specific problem in hand, e.g. by substituting the relevant quantities into the formula. Correct application of a formula without the formula being quoted obviously earns the M mark and in some cases an M mark can be implied from a correct answer. A Accuracy mark, awarded for a correct answer or intermediate step correctly obtained. Accuracy marks cannot be given unless the associated method mark is earned (or implied). B Mark for a correct result or statement independent of method marks. DM or DB When a part of a question has two or more ‘method’ steps, the M marks are generally independent unless the scheme specifically says otherwise; and similarly, when there are several B marks allocated. The notation DM or DB is used to indicate that a particular M or B mark is dependent on an earlier M or B (asterisked) mark in the scheme. When two or more steps are run together by the candidate, the earlier marks are implied and full credit is given. FT Implies that the A or B mark indicated is allowed for work correctly following on from previously incorrect results. Otherwise, A or B marks are given for correct work only.  A or B marks are given for correct work only (not for results obtained from incorrect working) unless follow through is allowed (see abbreviation FT above).  For a numerical answer, allow the A or B mark if the answer is correct to 3 significant figures or would be correct to 3 significant figures if rounded (1 decimal place for angles in degrees).  The total number of marks available for each question is shown at the bottom of the Marks column.  Wrong or missing units in an answer should not result in loss of marks unless the guidance indicates otherwise.  Square brackets [ ] around text or numbers show extra information not needed for the mark to be awarded.

9231/12 Cambridge International AS & A Level – Mark Scheme PUBLISHED May/June 2023 © UCLES 2023 Page 5 of 16 Abbreviations AEF/OE Any Equivalent Form (of answer is equally acceptable) / Or Equivalent AG Answer Given on the question paper (so extra checking is needed to ensure that the detailed working leading to the result is valid) CAO Correct Answer Only (emphasising that no ‘follow through’ from a previous error is allowed) CWO Correct Working Only ISW Ignore Subsequent Working SOI Seen Or Implied SC Special Case (detailing the mark to be given for a specific wrong solution, or a case where some standard marking practice is to be varied in the light of a particular circumstance) WWW Without Wrong Working AWRT Answer Which Rounds To

9231/12 Cambridge International AS & A Level – Mark Scheme PUBLISHED May/June 2023 © UCLES 2023 Page 6 of 16 Question Answer Marks Guidance 1(a) 6 0 2 0 2 3 2 2 3 1 2                 A so true when 1. n  B1 States base case. Assume that it is true for n k  , so 2 3 0 2 3 1 2 k k k           A . B1 States inductive hypothesis. Then 1 1 1 2 3 0 3 0 2 3 0 2 1 1 3 1 2 3 3 2 2 k k k k k                                A M1A1 Multiplies 2 k A with A . So, it is also true for 1 n k  . Hence, by induction, true for all positive integers. A1 States conclusion. 5 1(b)   1 2 3 0 det det 3 3 1 1 n n n n            A Or a multiple of 1 2 0 2 3 1 3 2 3 n n n n            A seen. B1   1 2 3 1 0 3 1 3 n n n n            A B1 OE 1 2 0 2 3 1 3 2 3 n n n n            A 2

9231/12 Cambridge International AS & A Level – Mark Scheme PUBLISHED May/June 2023 © UCLES 2023 Page 7 of 16 Question Answer Marks Guidance 2(a) 2 ( 4) 2(6)   M1 Uses formula for sum of squares. 4 A1 2 2(b)   2 2 2 2 r r r        B1 Expands.           2 2 2 2 1 1 4 2( 4) 3 n n r r r r r r r                 M1 A1 Collects like terms and uses 4       and their result from part (a).      1 2 4 4 1 1 2 1 n n n n n n      M1 Applies formulae from MF19.          1 2 1 2 5 1 2 2 2 2 2 4 1 2 1 4 2 3 1 n n n n n n n n n n n             M1 A1 Simplifies. 6

9231/12 Cambridge International AS & A Level – Mark Scheme PUBLISHED May/June 2023 © UCLES 2023 Page 8 of 16 Question Answer Marks Guidance 3(a) 1 ( 1) 1 1 1 ( )( 1 1 1 1) k kr kr k k r kr               M1 A1 Finds partial fractions. 1 1 1 1 1 1 1 1 1 1 1 ( 1)( 1) 2 1 1 ( 1) 1 n r k k k n k kr kr n k k k                         M1 Writes at least three complete terms, including last. 1 1 1 1 k kn         A1 OE e.g. 1 n kn  4 3(b) 1 k B1 1 3(c) 2 2 1 1 1 1 1 1 ( 1)( 1) ( 1)( 1) ( 1)( 1) n n n r n r r kr kr k kr kr k kr kr k                   M1 Or applies the method of differences again. 2 2 1 1 1 1 1 1 1 1 1 1 1 1 ( 1) ( 1) k k k kn kn n k n                              A1 OE e.g. 2 2 ( 1) ( 1) 1 1 n n k n kn      2

9231/12 Cambridge International AS & A Level – Mark Scheme PUBLISHED May/June 2023 © UCLES 2023 Page 9 of 16 Question Answer Marks Guidance 4(a) 2 2 cos sin sin cos a b c a                     M1 Uses correct matrix for rotation. 2 2 b c  which is impossible since b and c are real and 0. b  A1 AG 2 4(b) 2 2 2 2 a b x ax b y y c a c x ay                      B1 Transforms x y       to . X Y         2 2 c x amx m ax b mx    M1 A1 Uses y mx  and Y mX  . 2 2 2 2 2 2 c am ma b m c b m      A1 c b y x  and c b y x  A1 5 4(c) 1 5 5 0 0 1 0 5          M M1 A1* Award M1 if matrices correct but order is wrong. 2 5 5 0 5       DA1 Dep: previous A1 3 4(d) 12 det  M M1 Using their . M 300 cm2 A1FT 2

9231/12 Cambridge International AS & A Level – Mark Scheme PUBLISHED May/June 2023 © UCLES 2023 Page 10 of 16 Question Answer Marks Guidance 5(a) B1* Correct shape and domain, polar graph with r strictly decreasing but condone if not strictly decreasing close to π  . DB1 Fully correct including shape at 0  correct shape at π  correct   l,0 B1 Identified as point furthest from the pole and given as coordinates. 3 5(b) π 1 2 2 0 1 1 d   M1 Uses correct formula with correct limits. π 1 0 1 2 tan       M1 A1 Integrates 2 1 1 .  1 2 1 π 0.631 tan  A1 4 0 

9231/12 Cambridge International AS & A Level – Mark Scheme PUBLISHED May/June 2023 © UCLES 2023 Page 11 of 16 Question Answer Marks Guidance 5(c) 2 1 sin y     B1 Uses sin y r       1 1 2 2 2 2 2 1 cos 1 d 0 s 1 in d y              M1 A1 Sets derivative equal to zero. 0 cot 1 0 1               A1 AG. 2 1 1 0 . co 1 1.1 t1.1 1 .0         … and cot1.2 1 0.209 1 1.2 1.2        … B1 Shows sign change (1sf or better). 5 Question Answer Marks Guidance 6(a) 2 x  B1 States vertical asymptote.    2 2 15 2 4 7 4 x x x x y x          M1 A1 Finds oblique asymptote. 3

9231/12 Cambridge International AS & A Level – Mark Scheme PUBLISHED May/June 2023 © UCLES 2023 Page 12 of 16 Question Answer Marks Guidance 6(b)       2 2 2 2 2 2 15 d d 2 x x x x y x x        M1 Differentiates. 2 4 11 0 x x      2 d 7 or 1 d 2 y x x           A1 Forms quadratic equation or simplifies d . d y x 2 4 4(1)(11) 28 0    (or ' 0 y  ) There are no turning points. A1 Correct conclusion. 3

9231/12 Cambridge International AS & A Level – Mark Scheme PUBLISHED May/June 2023 © UCLES 2023 Page 13 of 16 Question Answer Marks Guidance 6(c) B1 Axes and asymptotes. B1 Branches correct.   (0,7.5), 5,0 ,(3,0)  B1 States coordinates of intersections with axes. 3

9231/12 Cambridge International AS & A Level – Mark Scheme PUBLISHED May/June 2023 © UCLES 2023 Page 14 of 16 Question Answer Marks Guidance 6(d) B1FT FT from sketch in (c). B1 Correct shape at infinity and on x axis. 2 6(e) 2 2 15 2 15 2 x x x     or 2 2 15 2 15 2 x x x     1 2 1 2 0 x x   or 2 19 2 30 0 x x    M2 Finds critical points, award M1 for each case. 11 2 0, x  or 5 2 12, x  A1 12 0 x    or 5 11 2 2 x   A1FT 4

9231/12 Cambridge International AS & A Level – Mark Scheme PUBLISHED May/June 2023 © UCLES 2023 Page 15 of 16 Question Answer Marks Guidance 7(a) 0 0 1 1 1 2 ~ 1 1 1 1 2 1             i j k M1 A1 Finds common perpendicular. ( 4) ( 3) 7 7 y z      M1 A1 Substitutes point. 4 7(b) States point common to both planes e.g. 7 2 . 5              B1 FT 2 0 1 1 5 5 3 5 5             i j k M1 A1FT Finds direction of line. 5 7 2 5 2 5                         r A1 OE. 4 7(c) 7 7 2 2 a a     M1 Uses correct formula for distance from A to 1 . 1 a  A1 2

9231/12 Cambridge International AS & A Level – Mark Scheme PUBLISHED May/June 2023 © UCLES 2023 Page 16 of 16 Question Answer Marks Guidance 7(d) 2 1 2 2 2 2 (1 ) 2 b b b b     M1 A1 Uses correct formula.   2 2 2 2 1 2 2 1 0 b b b b b       M1 Solves for b. 1 2 b  A1 CAO 4