It is given that ∑ (from r=1 to n) u_r = n²(2n + 3), where n is a positive integer.
- (i)Find ∑ (from r=n+1 to 2n) u_r.[2]
- (ii)Find u_n.[3]
Mark scheme
Marking points from the official mark scheme (May/June 2017). The mark or mark type is shown in brackets.
- [M1] Method mark for using S2n - Sn
- [A1]
- [M1A1] Method mark for using Sn – Sn-1 OE
- [A1] SR: CAO B1 without wrong working
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