Date | May 2021 | Marks available | 5 | Reference code | 21M.1.SL.TZ1.3 |
Level | Standard Level | Paper | Paper 1 (without calculator) | Time zone | Time zone 1 |
Command term | Find | Question number | 3 | Adapted from | N/A |
Question
Consider an arithmetic sequence where u8=S8=8. Find the value of the first term, u1, and the value of the common difference, d.
Markscheme
METHOD 1 (finding u1 first, from S8)
4(u1+8)=8 (A1)
u1=-6 A1
u1+7d=8 OR 4(2u1+7d)=8 (may be seen with their value of u1) (A1)
attempt to substitute their u1 (M1)
d=2 A1
METHOD 2 (solving simultaneously)
u1+7d=8 (A1)
4(u1+8)=8 OR 4(2u1+7d)=8 OR u1=-3d (A1)
attempt to solve linear or simultaneous equations (M1)
u1=-6, d=2 A1A1
[5 marks]
Examiners report
[N/A]