Ch3- Sequences & Series

Question 1

nth term of an arithmetic sequence

Answer 1

uⁿ = a + (n-1)d

Question 2

sum of n terms for arithmetic

Answer 2

Sⁿ = n/2 (2a + (n-1)d)
// n/2 (a + L)

L = last term

also learn proof (Sn + Sn)

Question 3

nth term of geometric

Answer 3

uⁿ = arⁿ‾¹

Question 4

sum of n terms for geometric

Answer 4

Sⁿ = a(1-rⁿ)/ 1-r

also learn proof (Sn = rSn)

Question 5

sum of ∞ terms for geometric

Answer 5

S∞ = a/ 1-r

Question 6

how to tell if geometric seq is convergent

Answer 6

if ∣r∣ < 1
S∞ = a/ 1-r