NATIONAL SENIOR CERTIFICATE GRADE 12 MATHEMATICS P1 SEPTEMBER 2014 MEMORANDUM MARKS: 150 This memorandum consists of 16 pages. Copyright reserved Please turn over Mathematics/P1 2 NSC – Memorandum NW/September 2014 NOTE: If a candidate answered a question TWICE, mark the FIRST attempt ONLY. If a candidate crossed out an attempt of a question and did not redo the question, mark the crossed out question. Consistent accuracy (CA) applies in ALL aspects of the memorandum. QUESTION 1 1.1 1.1.1 1.1.2 1.1.3 2𝑥 2 − 7𝑥 + 3 = 0 (2𝑥 − 1)(𝑥 − 3) = 0 2𝑥 = 1 or 𝑥 = 3 1 𝑥= 2 Factors 1 𝑥= 2 𝑥=3 (3) 2 17𝑥 − 8 = 3𝑥 0 = 3𝑥 2 − 17𝑥 + 8 −𝑏±√𝑏2 −4𝑎𝑐 𝑥= 2𝑎 −(−17)±√(−17)2 −4(3)(8) = 2(3) 17±√193 = 6 𝑥 = 5,15 or 𝑥 = 0,52 (2𝑥 − 3)(4 − 𝑥) ≥ 0 3 Critical values: 𝑥 = 2 or 𝑥 = 4 Standard form Substitution into formula Simplify Each value of x (5) Critical values − − −0 + + + + + + + + + 0 − − − 3 2 4 3 ∴ ≤𝑥 ≤4 2 3 𝑥≥2 𝑥≤4 (3) OR (2𝑥 − 3)(4 − 𝑥) ≥ 0 3 Critical values: 𝑥 = 2 or 𝑥 = 4 Critical values 3 2 ∴ 4 3 2 ≤𝑥 ≤4 3 𝑥≥2 𝑥≤4 OR Copyright reserved (3) Please turn over Mathematics/P1 3 NSC – Memorandum (2𝑥 − 3)(𝑥 − 4) ≤ 0 3 Critical values: 𝑥 = 2 or 𝑥 = 4 NW/September 2014 Critical values o 3 2 ∴ 4 3 2 3 𝑥≥2 𝑥≤4 ≤𝑥 ≤4 (3) 1.2 1.2.1 1.2.2 4𝑎+𝑏 = 2𝑏+4 22𝑎+2𝑏 = 2𝑏+4 ∴ 2𝑎 + 2𝑏 = 𝑏 + 4 𝑏 = 4 − 2𝑎 2 2𝑎 − 3𝑎𝑏 = −4 Substitute 𝑏 = 4 − 2𝑎 2𝑎2 − 3𝑎(4 − 2𝑎) = −4 2𝑎2 − 12𝑎 + 6𝑎2 = −4 8𝑎2 − 12𝑎 + 4 = 0 2𝑎2 − 3𝑎 + 1 = 0 (2𝑎 − 1)(𝑎 − 1) = 0 1 𝑎 = 2 or 𝑎 = 1 1 𝑏 = 4 − 2 (2) or 𝑏=3 or 1.3 Exponential law Equate exponents (2) Substitute 𝑏 = 4 − 2𝑎 Standard form Factors Both values of a 𝑏 = 4 − 2(1) 𝑏=2 Both values of b (5) (0,04)0,5 4 =( 100 1 2 ) 1 =√ = = 4 100 OR 2 2 2 [(10) ] Simplify 2 10 1 Answer (2) 5 1 (If ± 5, penalise 1 mark) Copyright reserved Please turn over Mathematics/P1 4 NSC – Memorandum NW/September 2014 1.4 Squaring 𝑦 2 = (√2 − 1)(√2 − 1) 𝑦 2 = 2 − 2√2 + 1 𝑦 2 = 3 − 2√2 ∴ 𝑦 = √3 − 2√2 ∴𝑦=𝑥 Expand Simplify OR 𝑥 = √3 − 2√2 = √2 − 2√2 + 1 = √(√2 − 1) Expand Bracket squared 2 = √2 − 1 ∴ 𝑥 = 𝑦 = √2 − 1 Simplify (3) [23] QUESTION 2 Expansion 20 2.1 ∑(15 − 4𝑛) = 3 + (−1) + (−5)+ . . . 𝑛=3 Substitute a and d into correct formula 𝑛 = 18 𝑎 = 3 , 𝑑 = −4 , 𝑛 = 18 S18 = 2.2 2.2.1 18 2 [2(3) + 17(−4)] = 9[−62] = −558 5 216 𝑙 ; 6 (216)𝑙 ; On 2nd day: T2 = 5 6 Answer 5 5 ( ) 216 𝑙 6 6 ( 216) = 180 𝑙 5 6 of 216 Answer (2) OR Day 2: T2 = 216 − 2.2.2 (4) 1 6 (216) = 180 𝑙 𝑎 = 216; On the 7th day: Tn = 𝑎𝑟 𝑛−1 216 − 1 6 Answer 5 𝑟= 6 (216) (2) a r 5 6 T7 = (216) ( 6 ) = 72,337 . . . ≈ 72,34 𝑙 Answer (2 dec.) (3) Copyright reserved Please turn over Mathematics/P1 2.3 2.3.1 5 NSC – Memorandum 2(3𝑥 − 1) + 2(3𝑥 − 1)2 + 2(3𝑥 − 1)3 + . . . Converge if −1 < 𝑟 < 1 ∴ −1 < 3𝑥 − 1 < 1 0 < 3𝑥 < 2 2 0<𝑥 < 3 NW/September 2014 −1 < 𝑟 < 1 𝑟 = 3𝑥 − 1 Answer (3) 2.3.2 Value of a Value of r 1 𝑎 = 2 (3 (2) − 1) = 1 1 1 𝑟 = 3 (2) − 1 = 2 𝑆∞ = = 𝑎 1−𝑟 Substitution into correct formula 1 1 1−(2) Answer (4) = 2 2.4 2 ; 𝑥−2 x ; 12 12 − 𝑥 12 − 𝑥 − (𝑥 − 2) ; y 𝑦 − 12 𝑦 − 12 − (12 − 𝑥) 2nd difference = 6 12 − 𝑥 − (𝑥 − 2) = 6 −2𝑥 + 14 = 6 −2𝑥 = −8 𝑥=4 Substitute 𝑥 = 4 into 𝑦 − 12 − (12 − 𝑥) = 6 𝑦 − 12 − (12 − 4) = 6 𝑦 − 20 = 6 𝑦 = 26 2nd difference Equation in terms of x 𝑥=4 Substitute into 2nd equation 𝑦 = 26 (5) [21] Copyright reserved Please turn over Mathematics/P1 3.1 6 NSC – Memorandum NW/September 2014 QUESTION 3 12 ℎ(𝑥) = +6 , 𝑥 >0 𝑥−4 Vertical asymptote: 𝑥 = 4 Horizontal asymptote: 𝑦 = 6 y-intercept: 𝑥 = 0 𝑦=3 12 x-intercept: 𝑦 = 0 +6=0 𝑥−4 12 = −6(𝑥 − 4) 6𝑥 = 12 𝑥=2 y h Both asymptotes Shape 𝑦=6 𝑦≠3 3o 𝑥=2 2 0 x (4) 𝑥=4 3.2 𝑘(𝑥) = −12 𝑥−4 −12, −4 −6 𝑥>0 – 6 , 𝑥>0 (3) [7] 4.1 4.1.1 QUESTION 4 𝑓(𝑥) = 2𝑥 2 − 6𝑥 − 20 −𝑏 −(−6) 3 Turning point: 𝑥 = 2𝑎 = 2(2) = 2 OR f’(x) = 4x – 6 Value of x 0 = 4x – 6 3 x = 2 3 3 3 −49 1 𝑦 = 𝑓 ( ) = 2( )2 − 6 ( ) − 20 = /−242 2 2 2 2 OR 𝑦 = 3 4𝑎𝑐−𝑏2 D(2 ; Copyright reserved 4𝑎 −49 2 = 4(2)(−20)−(−6)2 4(2) = −49 2 Value of y (2) 1 /−242 3 ) OR D ( 2 ; −24,5) Please turn over Mathematics/P1 4.1.2 4.1.3 4.1.4 7 NSC – Memorandum 2𝑥 2 − 6𝑥 − 20 = 0 𝑥 2 − 3𝑥 − 10 = 0 (𝑥 − 5)(𝑥 + 2) = 0 𝑥 = 5 or 𝑥 = −2 A(−2 ; 0 ) B(5 ; 0 ) 𝑔(𝑥) = −2𝑥 + 𝑘 Substitute (−2 ; 0): 0 = −2(−2) + 𝑘 𝑘 = −4 2𝑥 2 − 6𝑥 + 𝑝 = 0 2𝑥 2 − 6𝑥 − 20 = −𝑝 − 20 ∴ −𝑝 − 20 < −24,5 −𝑝 < −4,5 𝑝 > 4,5 NW/September 2014 𝑓(𝑥) = 0 Factors Both coordinates (3) Substitute 𝑥 = −2 Answer (2) Change to 𝑓(𝑥) Answer (2) OR 2𝑥 2 − 6𝑥 + 𝑝 = 0 For non-real roots ∆< 0 𝑏 2 − 4𝑎𝑐 < 0 (−6)2 − 4(2)(𝑝) < 0 36 − 8𝑝 < 0 −8𝑝 < −36 𝑝 > 4,5 36 − 8𝑝 < 0 Answer (2) OR 4.1.5 For no point of intersection f must be shifted more than 24,5 units upwards. ∴ y-intercept will move 20 + 4,5 units upwards . ∴ 𝑝 > 4,5 𝑓(𝑥). 𝑔(𝑥) ≤ 0 𝑥 = −2 or 𝑥 ≥ 5 Answer only (2) 𝑥 = −2 𝑥≥5 (2) 4.1.6 𝑦 = −2𝑥 + 𝑡 −2𝑥 + 𝑡 = 2𝑥 2 − 6𝑥 − 20 0 = 2𝑥 2 − 4𝑥 − 20 − 𝑡 Tangent if roots are equal: ∆= 0 (−4)2 − 4(2)(−20 − 𝑡) = 0 16 + 160 + 8𝑡 = 0 8𝑡 = −176 𝑡 = −22 OR 𝑓 ′ (𝑥) = 4𝑥 − 6 𝑚𝑡 = −2 ∴ 4𝑥 − 6 = −2 4𝑥 = 4 𝑥=1 𝑦 = 𝑓(1) = −24 ∴ −24 = −2(1) + 𝑡 𝑡 = −22 Copyright reserved Equate Standard form ∆= 0 Answer (4) 𝑓 ′ (𝑥) = −2 𝑥=1 𝑦 = −24 𝑡 = −22 (4) Please turn over Mathematics/P1 4.2 4.2.1 8 NSC – Memorandum 𝑝(𝑥) = 𝑥 2 + 1 and 𝑟(𝑥) = 𝑥 2 + 2𝑥 𝑝(𝑥 + 1) − 2 = (𝑥 + 1)2 + 1 − 2 = 𝑥 2 + 2𝑥 + 1 + 1 − 2 = 𝑥 2 + 2𝑥 = 𝑟(𝑥) Shift p 1 unit to the left and 2 units downwards. NW/September 2014 (𝑥 + 1) −2 Explanation (3) 4.2.2 (If you replace x with 𝑥 + 1 you are shifting the graph 1 unit to the left and when subtracting 2 you are shifting the graph 2 units down) 𝑦 ∈ [1 ; ∞) 𝑦≥1 (1) OR 𝑦 ≥ 1 ,𝑦 ∈ 𝑅 [19] 5.1 QUESTION 5 (1; 4) or (2; 16) Any one point (1) 5.2 𝑓(𝑥) = 𝑎𝑥 2 Substitute inverse point: (1; 4) OR 2 4 = 𝑎(1) 𝑎=4 (2; 16) 16 = 𝑎(2)2 4𝑎 = 16 𝑎=4 ∴ 𝑓(𝑥) = 4𝑥 2 , 𝑥 ≥ 0 Substitute correct coordinate Equation 𝑓(𝑥) 𝑥≥0 (3) OR Substitute (4; 1) or (16; 2) into 𝑥 = 𝑎𝑦 2 : 4 = 𝑎(1)2 OR 16 = 𝑎(2)2 4=𝑎 16 = 𝑎. 4 4=𝑎 ∴ 𝑓(𝑥) = 4𝑥 2 , 𝑥 ≥ 0 Substitute correct coordinates Equation 𝑓(𝑥) 𝑥≥0 (3) 5.3 5.4 𝑔(𝑥 + 2) = 16 4𝑥+2 = 16 4𝑥+2 = 42 ∴ 𝑥+2=2 𝑥=0 2<𝑥≤3 Copyright reserved Substitution into 𝑔(𝑥) Same base 𝑥=0 (3) 𝑥>2 𝑥≤3 (2) [9] Please turn over Mathematics/P1 9 NSC – Memorandum NW/September 2014 QUESTION 6 6.1 (1 + 𝑖(4) 4 ) 4 1+ 𝑖(4) 4 𝑖(4) 4 = (1 + 0,14 12 ) 12 4 0,14 12 ) 12 4 12 = √(1 + 0,14 = √(1 + ) 12 𝑖(4) Substitution into formula −1 Simplification = 0,03540 . . . 4 𝑖4 = 0,141639 . . . Quarterly rate = 14,16 % Answer (3) 6.2 R3 500 + R5 700 T0 T1 T2 7% p.a. quarterly T3 T4 8% p.a. monthly A T5 (1 + 𝐴 = 𝑃(1 + 𝑖)𝑛 = 3 500 (1 + 0,07 8 4 ) (1 + 0,08 36 12 ) + 5 700 (1 + = 5 107,73273. . . + 6 685,4612 . . . = 𝑅 11 793,1939 . . . ≈ 𝑅 11 793,19 0,08 24 12 ) (1 + 0,07 8 ) 4 0,08 36 12 ) 5 700 (1 + 0,08 24 ) 12 Answer (4) [7] Copyright reserved Please turn over Mathematics/P1 7.1 10 NSC – Memorandum NW/September 2014 QUESTION 7 Calculate monthly payment for Option 1: P= 950 000 x T0 T1 T240 𝑖= Option 1: 𝑃 = x 0,12 12 = 0,01 𝑥[1−(1+𝑖)−𝑛 ] 𝑖 950 000 = 𝑥= = 𝑥[1−(1,01)−240 ] 0,01 950 000 . 0,01 [1−(1,01)−240 ] Simplify 9 500 0,908 184 . . . = 10 460,3182. . . ≈ 𝑅 10 460,32 Total cost for Option 1: Option 1 = 10 460,32 × 240 + 6 000 = 𝑅 2 516 476,80 7.2 Substitution into correct formula 0,12 𝑖 = 12 = 0,01 𝑛 = 240 Total cost for Option 2: Option 2 = 10 328,16 × 240 + 200 × 240 = 𝑅 2 526 758,40 Option 1 is the best. By choosing option 1 he will save R10 281,60. Answer Calculation Answer (7) 200 × 240 Answer Conclusion (3) [10] Copyright reserved Please turn over Mathematics/P1 11 NSC – Memorandum NW/September 2014 QUESTION 8 Note: Penalise only once for notation. 8.1 𝑓 ′ (𝑥) = lim 𝑓(𝑥+ℎ)−𝑓(𝑥) ℎ→0 = lim Formula ℎ 3−(𝑥+ℎ)2 − (3− 𝑥 2 ) Substitution ℎ ℎ→0 2 3−𝑥2 −2𝑥ℎ−ℎ −3 + 𝑥2 ℎ ℎ→0 = lim 2 = −2𝑥ℎ− ℎ lim ℎ ℎ→0 = ℎ(−2𝑥− ℎ) lim ℎ ℎ→0 Simplify Factorise = lim (−2𝑥 − ℎ) ℎ→0 Answer (5) = −2𝑥 8.2 8.2.1 𝑦= 2 3 √𝑥 = 2𝑥 𝑑𝑦 𝑑𝑥 − 𝜋𝑥 −1 3 = 2 .− = − 8.2.2 8.3 2𝑥 − 𝜋𝑥 2 3 1 3 . 𝑥 −4 3 −1 3 − 𝜋 4 𝑥− 3 – 𝜋 − 2 3 −𝜋 4 𝑥− 3 (3) 2 𝑥𝑦 − 𝑦 = 𝑥 − 1 𝑦(𝑥 − 1) = 𝑥 2 − 1 (𝑥−1)(𝑥+1) 𝑦= (𝑥−1) 𝑦=𝑥+1 𝑑𝑦 =1 𝑑𝑥 𝑓(𝑥) = 𝑥 2 − 10𝑥 + 25 𝑚𝑡 = 𝑓 ′ (𝑥) −8 = 2𝑥 − 10 2𝑥 = 2 𝑥=1 Factorise LHS Factorise RHS Simplify Answer (4) Multiply brackets 𝑓 ′ (𝑥) 𝑚𝑡 = −8 Answer (4) [16] Copyright reserved Please turn over Mathematics/P1 9.1 9.1.1 12 NSC – Memorandum QUESTION 9 𝑓(𝑥) = 𝑥 3 + 𝑝𝑥 2 + 𝑞𝑥 + 30 At turning point 𝑓 ′ (𝑥) = 0: 3𝑥 2 + 2𝑝𝑥 + 𝑞 = 0 Substitute 𝑥 = −1: 3(−1)2 + 2𝑝(−1) + 𝑞 = 0 3 − 2𝑝 + 𝑞 = 0 −2𝑝 + 𝑞 = −3 - - - (i) 𝑓′(𝑥) Substitute 𝑥 = −1 Equation (i) Substitute (−1; 36) in 𝑓(𝑥): (−1)3 + 𝑝(−1)2 + 𝑞(−1) + 30 = 36 −1 + 𝑝 − 𝑞 + 30 = 36 𝑝 − 𝑞 = 7 - - - (ii) −𝑝 = 4 𝑝 = −4 Substitute 𝑝 = −4 into (ii): −4 − 𝑞 = 7 𝑞 = −11 (i) + (ii): 9.1.2 9.1.3 NW/September 2014 Substitute (−1; 36) Equation (ii) 𝑝 = −4 𝑞 = −11 (7) At C: 𝑓(𝑥) = 𝑔(𝑥) = 36 𝑥 3 − 4𝑥 2 − 11𝑥 + 30 = 36 𝑥 3 − 4𝑥 2 − 11𝑥 − 6 = 0 But 𝑥 = −1 at A ∴ (𝑥 + 1)(𝑥 2 + 𝑘𝑥 − 6) = 0 𝑘 + 1 = −4 OR touching point at A 𝑘 = −5 ∴ (𝑥 + 1)(𝑥 + 1)(𝑥 − 6) = 0 ∴ (𝑥 + 1)(𝑥 2 − 5𝑥 − 6) = 0 ∴ (𝑥 + 1)(𝑥 + 1)(𝑥 − 6) = 0 𝑥=6 C (6; 36) 𝑓(𝑥) = 36 𝑥 + 1 factor 𝑥=6 (3) 𝑥 = −1 𝑦 = 26 Turning point of k: (−1; 26) (2) 9.2 (5; 4) x ℎ (2; -3) 2 5 x 𝑦 = ℎ′ (𝑥) Shape 𝑥=2 𝑥=5 (3) [15] Copyright reserved Please turn over Mathematics/P1 13 NSC – Memorandum NW/September 2014 QUESTION 10 10.1 y h 0 P S Q 6 R P(𝑥; 𝑥 2 ) and Q (𝑥; 0) QR = 6 − 𝑥 PQ = 𝑥 2 Area of PQRS = PQ × QR = 𝑥 2 × (6 − 𝑥) = 6𝑥 2 − 𝑥 3 10.2 For maximum area: 𝑑𝐴 𝑑𝑥 x QR = 6 − 𝑥 PQ = 𝑥 2 Method (3) =0 12𝑥 − 3𝑥 2 = 0 3𝑥(4 − 𝑥) = 0 𝑥 = 0 or 𝑥 = 4 N/A Maximum area = 6(4)2 − (4)3 = 32 units2 12𝑥 − 3𝑥 2 𝑑𝐴 =0 𝑑𝑥 𝑥=4 Answer (4) [7] Copyright reserved Please turn over Mathematics/P1 11.1 14 NSC – Memorandum NW/September 2014 QUESTION 11 C- correct W- wrong C 0,7 C 0,6 0,3 Tree diagram W C 0,4 0,4 W 0,6 W 11.2 P(2nd answer correct) = P(CC) + P(WC) = (0,6 × 0,7) + (0,4 × 0,4) = 0,42 + 0,16 = 0,58 OR = 58% 𝑃(𝐴 ∩ 𝐵) = 𝑃(𝐴) × 𝑃(𝐵) 0,1 = (𝑥 + 0,1) × (0,1 + 0,3) 0,1 = (𝑥 + 0,1) × (0,4) 0,1 = 0,4𝑥 + 0,04 0,06 = 0,4𝑥 0,06 𝑥= 0,4 Sum of probabilities Substitution Answer 𝑃(𝐴 ∩ 𝐵) = 𝑃(𝐴) × 𝑃(𝐵) Substitution 𝑥 = 0,15 Value of x 𝑥 + 0,1 + 0,3 + 𝑦 = 1 ∴ 0,15 + 0,1 + 0,3 + 𝑦 = 1 𝑦 = 0,45 11.3.1 11.3.2 11.3.3 12! = 12 × 11 × 10 ×. . . × 3 × 2 × 1 = 479 001 600 8 and 11 can be arranged in 2! different ways. Consider 8 and 11 as an entity. 11 objects can be arranged in 11! different ways. Total arrangements = 2! × 11! = 2 × (11 × 10 × 9 × 8 × 7 × 6 × 5 × 4 × 3 × 2 × 1) = 2 × 39 916 800 = 79 833 600 4! 4×3×2×1 = = 4 × 3 = 12 2! 2×1 OR 4 × 3 = 12 TOTAL: Copyright reserved (4) Sum of probabilities is 1 Value of y (5) 12! Answer (2) 2! 11! Answer (3) 4! ÷ 2! Answer (2) Answer only, full marks. [16] 150 Please turn over Mathematics/P1 15 NSC – Memorandum NW/September 2014 ANALYSIS OF QUESTION PAPER: MATHEMATICS PAPER: 1 Question Nr Concept 1.1 1.1.1 1.1.2 1.1.3 Equations Factorisation Formula Inequality 1.2 1.2.1 1.2.2 Simultaneous Equations Exponential Equation Simultaneous Equations 1.3 1.4 Exponents Surds 2 2.1 2.2.1 2.2.2 2.3.1 2.3.2 2.4 Sequences and Series Sigma notation Geometric sequence 3 3.1 3.2 Hyperbola Sketch Reflection 4 4.1.1 4.1.2 4.1.3 4.1.4 4.1.5 4.1.6 4.2 4.2.1 4.2.2 Quadratic function Turning point X-intercept Equation line Infinite series Level 1 Knowledge Level 2 Routine Procedures DATE: Sept 2014 Level 3 Complex Procedures Level 4 Problem Solving 3 5 3 2 5 2 3 4 2 3 3 4 Quadratic number pattern Copyright reserved 5 4 3 2 3 2 2 2 4 3 1 Please turn over Mathematics/P1 Question Nr Concept 5 5.1 5.2 5.3 5.4 Inverse 6 6.1 6.2 Financial Mathematics 7.1 7.2 Loans 8 8.1 8.2.1 8.2.2 8.3 Differential Calculus 9 9.1.1 9.1.2 9.1.3 9.2 Cubic Function Equation Coordinate Transformation Application 10.1 10.2 Application 11 11.1 11.2 11.3.1 11.3.2 11.3.3 Probability 16 NSC – Memorandum Level 1 Knowledge NW/September 2014 Level 2 Routine Procedures Level 3 Complex Procedures Level 4 Problem Solving 1 3 3 2 3 4 7 3 5 3 4 4 7 3 2 3 3 4 4 5 2 3 2 TOTAL: % Copyright reserved 26 17,3 52 34,7 51 34 21 14