Question

Nilai dari
2+5+8+...+89=... plus caranya

Answer 1

Un = a + (n-1) b
89 = 2+(n-1) 3
89 = 2+3n-3
89 = -1 + 3n
90 = 3n
n = 30

S30 = 30/2 (2.2+(30-1) 3)
S30 = 15 (4+87)
S30 = 15.91
S30 = 1365
Jadi, hasilnya 1365 ^^

Answer 2

Un = a +(n-1)b
Un = 2 +(n-1)3
Un = 2 + 3n -3
Un= 3n -1

89 = 3n -1
90 = 3n
n  = 30

jadi semua angka nya = 30

2 + 5 + 8 +.... + 89
89+86+83+.....+ 2 +
91 +91+91.....+91
91 x 30
2730

lalu 2730 :2 = 1365