tentukan jumlah 10 suku pertama dari barisan 6,11,16,21

Sn = n/2 (2a+(n-1)b)
a = U1 = 6
b = beda = 5

S10 = 10/2 (2.6+(10-1)5)
S10 = 5 (12+9.5)
S10 = 5 (12+45)
S10 = 5 x 57
S10 = 285

Maaf bila ada kesalahan

Aritmatika

a = 6

b = U2 - U1
b = 11 - 6
b = 5

Sn = n/2 (2a + (n - 1)b)
S10 = 10/2 (2.6 + 9.5)
S10 = 5 (12 + 45)
S10 = 5 (57)
S10 = 285

semoga berguna +_+