Question

Tentukan banyak suku dan jumlah barisan aritmetika-12-8-4-0+...+128

Answer 1

-12,-8,-4,0,.....,128
a= -12
b= -8 -(-12 = 4

banyak suku
un = a + (n - 1)b
128 = -12 + (n -1) x 4
128 = - 12 + 4n - 4
128 = -16 + 4n
128 + 16 = 4n
144 = 4n
n= 36 bilangan

jumlah barisan
Sn = n/2 (a + un)
Sn = 36/2 (-12 + 128)
Sn = 18 x 116
Sn = 2088