MATHEMATICS
PAPER 1
GRADE 12
NSC EXAMS PAST PAPERS AND MEMOS JUNE 2019
NOTE: - If a candidate answered a question TWICE, mark the FIRST attempt ONLY.
- Consistent accuracy(CA) applies in ALL aspects of the marking guideline.
- If a candidate crossed out an attempt of a question and did not redo the question, mark the crossed-out attempt.
- The mark for substitution is awarded for substitution into the correct formula.
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MEMORANDUM
QUESTION 1
1.1.1 | x2 - 7x = 0 x(x + 7) = 0 x = 0 or x + 7 = 0 x = -7 | ✔ both factors ✔ both x-values (2) |
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1.1.2 | Penalise 1 mark for incorrect rounding off. 5 - 10x - 3x2 = 0
∴ x = 0,44 or x = -3,77 | ✔ substitution ✔✔ x-values (3) |
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1.1.3 | (2x - 1)(4 - x) ≥ 0 (2x - 1)(x - 4) ≤ 0 | ✔ critical values ✔✔ answer (accuracy) (3) |
1.1.4 | | ✔ squaring both sides ✔ multiplication ✔ standard form ✔ factors ✔ answers (5) |
1.2 | y = -3x + 2.................(1) x2 + y = xy + x ............(2) (1) in (2): x2 + (-3x + 2) = x(-3x + 2) + x x2 - 3x + 2 = -3x2 + 2x + x 4x2 - 6x + 2 = 0 2x2 - 3x + 1 = 0 (2x - 1)(x - 1) = 0 x = ½ or x = 1 y = ½ or y = -1 | ✔ substitution ✔ standard form ✔ factors ✔ x-values ✔ y-values (5) |
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1.3.1 | | ✔ factors under root ✔ simplification (this step must be seen) ✔ answer (3) |
1.3.2 | | ✔ equation (3) ✔ substitution ✔ simplification ✔ simplification ✔ isolating a (5) |
QUESTION 2
2.1.1 | 12 ; 9 ; 6 ; . . . . . a = 12 and d = –3 Tn = 12 + (n - 1)(-3) = -3n + 15 | ✔ d = –3 ✔ answer (2) |
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2.1.2 | Tn = -3(40) + 15 = -105 | ✔ substitution ✔ answer (2) |
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2.1.3 | S40 = 40/2 (12 + (-105)) = -1860 | ✔ substitution ✔ answer (2) |
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2.2.1 | Quadratic Pattern : T1 = 10 1st difference pattern : -7; -5; -3;... ∴ T2 = 3 and T3 = -2 | ✔ first differences ✔ ✔ answers (T1 and T2 ) (3) |
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2.2.2 | 2a = 2 3a + b = -7 a + b + c = 10 a = 1 3(1) + b = -7 (1) + (-10) + c = 10 b = -10 c = 19 ∴Tn = n2 - 10n +19 | ✔ value of a ✔ value of b ✔ value of c (✔✔✔can be awarded at formula) (3) |
2.2.3 | n2 - 10n + 19 = 2019 n2 - 10n - 2000 = 0 (n - 50)(n + 40) = 0 n = 50 or n = 40 ∴T50 = 2019 | ✔ equation ✔ factors ✔ answer (T50) (3) |
2.3.1 | Sn = 81 - 81(3)-n T1 = S1 = 81 - 81(3)-n = 54 | ✔ answer (1) |
2.3.2 | | ✔ T2 = 18 ✔ r = 1/3 ✔ answer (3) |
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2.3.3 | Yes. r = - 1 < 1/3 < 1 ; r ≠ 0 | ✔ YES ✔ reason (2) |
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2.3.4 | S∞ = a or S∞ =81 - 81(3)-∞ 1 - r = 54 = 81 1 - 1/3 = 81 - 81(1/3)∞ = 81 | ✔ substitution ✔ answer (2) |
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2.4 | 6x + 18 + 12096 = 0 6x = -12114 x = -2019
| ✔ (2x + 3 + 2x + 6 + 2x + 9) ✔ sum of GS ✔ simplification ✔ answer (4) |
| | [27] |
QUESTION 3
3.1 | (let y = 0) 2 +1 = 0 x - 1 2 = -1 x - 1 2 = -x + 1 x = -1 (-1 : 0) Or (let x= 0) y = 2 + 1 0 -1 y = -2 + 1 y = -1 (0 ; -1) | ✔ substitution (y = 0) ✔ substitution (x = 0) ✔ coordinates of A ✔ coordinates of B (4) |
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3.2 | x =1 | ✔ answer (1) |
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3.3 | y ∈ R\{1} OR y ∈ R but y # 1 | ✔ answer (1) |
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3.4 |
∴AB = 4 units
| ✔ coordinates of A and B ✔ substitution ✔ simplification ✔ answer (4) |
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3.5 | h(x) = - 2 + 1 (x + 5) | ✔ – ve (reflection) ✔ (x – 5) (shift ) (2) |
| | [12] |
QUESTION 4
4.1 | | Parabola ✔ x-intercepts ✔ Turning point ✔ Axis of symmetry ✔ Shape Straight line ✔ x-intercept ✔ y-intercept (6) |
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4.2 | From sketch −1 < x < 0 or x∈−(-1 ; 0) Algebraic solution
-2x2 - 2x > 0 -2x(x + 1) > 0 2x(x + 1) < 0 Cv: -1 < x < 0 | ✔✔ answer (2) |
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4.3 | ST = -2x2 - 2x - (3x - 3) = -2x2 - 5x + 3 ST'(x) = -4x - 5 = 0 -4x = 5
| ✔ ST = –2x2 – 2x – (3x – 3) ✔ ST’ = 0 ✔ x = -5/4 ✔answer (4) |
| | [12] |
QUESTION 5
5.1 | f(x) = 2x k = 2-3 k = 1/8 | ✔ substitution ✔ answer (2) |
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5.2 | f-1(x) : x = 2y y = log2x g-1(x) : x = 2y + 1 x - 1 = 2y y = ½x - ½ | ✔ interchanging x and y ✔ answer ✔ interchanging x and y ✔ answer (4) |
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5.3 | f'(x).g(x) ≤ 0 f'(x) is always +ve g(x) is -ve for x < -½ +ve for x > -½ ∴x ≤ -½ | ✔ method ✔ answer (2) |
| | [8] |
QUESTION 6
6.1 | | ✔ substitution ✔ answer (2) |
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6.2 | | ✔ substitution ✔ simplification ✔ answer (3) |
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6.3.1 | ∴effective rate = 6,70%
| ✔ formula ✔ substitution ✔ answer (3) |
6.3.2 | x= R997500,00 | ✔ ✔ equation (= 2 000 000) ✔ making x subject of the formula ✔ answer (5) |
| | [13] |
QUESTION 7
Penalise 1 mark for incorrect notation in the question
7.1 | f(x) = 5x2 - 5x f(x +h) = 5(x + h)2 - 5(x + h) = 5(x2 + 12xh + h2) - 5x - 5h = 5x2 + 10xh +5h2 - 5x - 5h
Answer only = 0 marks | ✔ 5x2 + 10xh +5h2 - 5x - 5h ✔ substitution ✔ simplification ✔ common factor ✔ answer (5) |
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7.2 | | ✔ (3) |
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7.3 | f(-1) = (-1)3 = -1 f(1) = (1)3 = 1
| ✔ f(-1) and f(1) ✔ substitution ✔ answer (3) |
| | [11] |
QUESTION 8
8.1.1 | f(x) = -(2x - 5)(x + 2)2 = 0 -2x + 5 = 0 or x + 2 = 0 ∴ x = 5/2 or x = -2 AB = 4,5 units | ✔ x-intercepts ✔ answer (2) |
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8.1.2 | f(x) = -2x3 - 3x2 + 12x + 20 f'(x) = -6x2 - 6x + 12 = 0 x2 + x - 2 = 0 (x + 2)(x - 1) = 0 x + 2 = 0 or x - 1 = 0 x = -2 or x = 1 T(1;y) | ✔ f'(x) ✔ factors ✔ correct x-value for T (3) |
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8.1.3 | mp = -6(-3)2 - 6(-3) + 12 = -24 y - y1 = m(x - x1) y - 11 = -24(x +3) y = -24x - 61 | ✔ gradient ✔ substitution ✔ answer (3) |
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8.1.4 | T(1 ; y) y = -2(1)3 - 3(1)2 + 12(1) + 20 = 27 ∴ 0 < k < 27 | ✔ max. value ✔✔ answer (accuracy) (3) |
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8.2.1 | c'(x) -3/2x2 + 6x = 0 x(-3/2x + 6) = 0 x =0 or x = 4 ∴0< x < 4 | ✔ equating to 0 ✔ factors ✔ answer (accuracy) (3) |
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8.2.2 | cn(x0 = -3 + 6 = 0 or x = 0 + 4 2 x = 2 x = 2 ∴ c(x) is concave up for x < 2 ∴ c(x) is concave down for x > 2 | ✔ method ✔ x-value ✔✔ conclusion/gevolgtrekking (4) |
| | [18] |
QUESTION 9
9.1 | h = 12 - 4x 3 | ✔✔ answer (2) |
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9.2 | | ✔ substitution ✔ answer ✔ derivative ✔ f'(x) = 0 ✔ answer ✔ answer (6) |
| | [8] |
QUESTION 10
10.1.1 | P(S) = 1
| ✔ 0,3 & 0,25 ✔ 0,35 & 0,25 ✔ 0,1 (3) |
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10.1.2 | P(A or B) = P(A) + P(B) - P(A and B) = 0,55 + 0,6 - 0,25 = 0,9 or (from sketch) P(A or B) = 0,3 + 0,25 + 0,35 = 0,9 | ✔ method ✔ answer (2) |
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10.1.3 | P(A and B') = 0,3 | ✔✔ answer (2) |
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10.1.4 | No : P(A ∩ B) = 0,25 ≠ 0 | ✔ answer (1) |
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10.1.5 | P(A ∪ B)' = 0,1 ≠ 0 No : or P(A ∪ B) = 0,9 ≠ 1 | ✔ answer (1) |
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10.2.1 | a = 20 b = (40 - x) | ✔ a = 20 ✔ b = (40 – x) (2) |
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10.2.2 | 79 - x + 20 + 19 - x + x + 11 + 16 + 40 - x = 173 -2x = 173 - 185 -2x = -12 x = 6 | ✔ equation ✔ answer (2) |
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10.2.3 | P (at least 2) = 20 + 11 + 16 + 6 173 = 53 / 0,31 / 30,6% 173 | ✔ adding correct values ✔ answer (2) |
| | [15] |
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| | TOTAL: 150 |