These are the first five terms of a sequence. 5 12 19 26 33 Find the next term of the sequence.
- (a)(i)These are the first five terms of a sequence. 5 12 19 26 33 Find the next term of the sequence.[1]
- (a)(ii)Find an expression for the nth term of the sequence.[2]
- (a)(iii)Tk and Tk+1 are consecutive terms of the sequence. The sum of these two terms is 703. Find the value of k.[3]
- (b)An expression for the nth term of a different sequence is n² + an+b . The 1st term of the sequence is 3. The 3rd term of the sequence is 19. Find the 6th term of the sequence.[5]
Mark scheme
Marking points from the official mark scheme (Oct/Nov 2023). The mark or mark type is shown in brackets.
- [1] (a)(i) 40
- [2] (a)(ii) 7n-2 oe final answer
- [2] (a)(ii) B1 for 7n+j oe seen, j may be 0
- [3] (a)(iii) 50
- [3] (a)(iii) M1 for correct equation for sum of terms
- [3] (a)(iii) FT use of their 7n-2
- [3] (a)(iii) M1 for correct rearrangement to ak = b, dependent on equation with two terms in k and a constant Not k + k + 1 = 703 oe
- [5] (b) 58
- [5] (b) B4 for a=4 and b=-2
- [5] (b) OR B2 for 1^2 + a + b = 3 or better and 3^2 + 3a + b = 19 or better or B1 for one correct
- [5] (b) M1 for correct method to eliminate one variable from their simultaneous equations
- [5] (b) M1 for 6^2 + their a x 6 + their b
- [5] (b) Alternative method
- [5] (b) B3 for second term = 10
- [5] (b) OR B1 for second difference = 2
- [5] (b) B2 for first pair of differences 7 and 9 or B1 for sum of first pair of differences = 16
- [5] (b) AND B1 for next first differences 11, 13, 15
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