Question

Jmlh suku pda deret 2+5+8+...+59 adalah..

tlng dijwb ya

Answer 1

Verified answer

A = 2
b = 3

Un = bn + a - b
59 = 3n + 2 - 3
59 = 3n - 1
3n = 59 + 1
3n = 60
  n = 60/3
  n = 20

Jadi, banyaknya suku barisan tersebut adalah 20

Answer 2

Verified answer

2 + 5 + 8 + ...+ 59
a = 2
b = 5 - 2 = 3
Un = a + (n - 1)b
59 = 2 + (n - 1) × 3
59 = 2 + 3n - 3
59 = 3n - 1
3n = 59 + 1
3n = 60
n = 60/3
n = 20

Sn = 1/2(n)[2a + (n - 1)b]
S20 = 1/2(20)[2(2) + (20 - 1) × 3]
S20 = 10[4 + 19 × 3]
S20 = 10[4 + 57]
S20 = 10 × 61
S20 = 610

Jadi jumlah pada deret itu adalah 610