FM - Core Pure 1 - 3) Series

Question 1

Formula to find sum of a series that doesn’t start at r=1

Answer 1

Σⁿ_r=k f(r) = Σⁿ_r=1 f(r) - Σ^k-1_r=1 f(r)

Question 2

Rearrange Σⁿ_r=1 kf(r) and Σⁿ_r=1 (f(r) + g(r))

Answer 2

• kΣⁿ_r=1 f(r)
• Σⁿ_r=1 f(r) + Σⁿ_r=1 g(r)

Question 3

Formula for the sum of a series of constant terms and of the first natural numbers

Answer 3

• Σⁿ_r=1 1 = n
• Σⁿ_r=1 r = n/2(n+1)