Hitunglah jumlah 30 suku pertama dari masing-masing barisan berikut a. 9,11,13,15,.... ,b. 150,147,144,141,.... , c. 2,7,12,17,....

a.
nilai a = 9
nilai b = 2
U30 = a + 29b
U30 = 9 + 29(2)
U30 = 67

Maka
S30 = n/2 (a + U30)
S30 = (30/2)(9 + 67)
S30 = 1140

#A
Dik. Barisan deret aritmatika : 9, 11, 13, 15... 
Dit. S30??

Jawab...

a  = 9
b = u2 - u1 = 11 - 9 = 2

Sn = n/2 (2a + (n-1) b)
S30 = 30/2 (2(9) + (29)(2))
S30 = 15 (18+58)
S30 = 15 (76)
S30 = 1140

#B
Dik. Barisan deret aritmatika : 150, 147, 144, 141... 
Dit. S30 ?

Jawab...

a = 150
b = u2 - u1 = 147 - 150 = -3

Sn = n/2 (2a + (n-1)b)
S30 = 30/2 (2(150) + (29) (-3))
S30 = 15 (300 - 87)
S30 = 15 (213)
S30 = 3a95

#C
Dik. Barisan deret aritmatika : 2,7, 12, 17, ...
Dit. S30 ?

Jawab...

a = 2
b = u2 - u1 = 7 - 2 = 5

Sn = n/2 (2a + (n - 1) b)
S30 = 30/2 (2(2) + (29)(5))
S30 = 15 (4 + 145)
S30 = 15 (149)
S30 = 2235

Semoga membantu... ^_^