Question

Carilah jumlah(Sn) untuk tiap deret berikut.
1+3+5+...+21
beserta cara

Answer 1

21 = U11
a = 1
b = U2-U1 = 2
Sn = n/2 (U1 + Un)
S11 = 11/2 (1 + U11)
S11 = 11/2 (1 + 21)
S11 = 11/2 (22)
S11 = 5,5 x 22
S11 = 121

Answer 2

1+3+5+...+21
suku 1 = 1
suku terakhir = 21
banyak suku = 11

(suku 1 + suku terakhir)/2 x banyak suku
= (1+21)/2 x 11
= 22/2 x 11
= 11 x 11
= 121