Question

1 +3+5+ ... + 17 hasilnya adalah

Answer 1

1+3+5+...+17
u1 = a = 1
u2 = 3
b = u2-u1 = 3-1 = 2

Un = a + (n-1)b
17 = 1 + (n-1)2
17 = 1+2n-2
17 = 2n-1
2n = 18
n = 9

Sn = n/2 (2a + (n-1)b)
S9 =9/2 (2*1 + (9-1)2)
S9 = 4,5 (2+ 16)
S9 = 4,5 * 18
S9 =81