2 marksThe Real Number System – ℝ
CAPE Pure Mathematics Unit 1 · May/June 2010 · Paper 2 · Question 2(a)(i)
Use the fact that Sₙ = ∑r = 1 to n of r = (1/2) n (n + 1) to express S₂ₙ = ∑r = 1 to 2n of r in terms of n.
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