Pure 3: Series

Question 1

Σr

Answer 1

1/2 n(n+1)

Question 2

Σkf(r)= ?

Answer 2

kΣf(r)

Question 3

Σ1 = ?

Answer 3

n

Question 4

Σ[f(r) + g(r)] = ?

Answer 4

Σf(r) + Σg(r)

Question 5

Σr^2 = ?

Answer 5

1/6 n(n+1)(2n+1)

Question 6

Σr^3 = ?

Answer 6

1/4 n^2 (n+1)^2