The nth term of a sequence is 2n+12n+12n+1. What is its fourth term?
A
r=1,2,3,4,5r=1,2,3,4,5r=1,2,3,4,5
B
A constant summed nnn times satisfies ∑r=1nc=cn\boxed{\displaystyle \sum_{r=1}^{n}c=cn}r=1∑nc=cn.
C
999
D
The standard sum of the first nnn positive integers is ∑r=1nr=n(n+1)2\boxed{\displaystyle \sum_{r=1}^{n}r=\frac{n(n+1)}{2}}r=1∑nr=2n(n+1).
1.7.3 Sigma notation (A-level only) Flashcards
Flashcards for AQA A Level Maths 1.7.3 Sigma notation (A-level only), covering the key formulae, methods and definitions you need to recall for Paper 1, Paper 2 and Paper 3. 21 cards, matched to the AQA A Level Maths (7357) specification. Recall questions account for roughly 50% of marks at A Level Maths, so these target the marks you can secure before the paper starts.