Pada suatu deret geometri diketahui suku ke-3 = 18 dan suku ke-6 = 486. suku pertama pada deret tersebut adalah...

1 answer:

3 0

A . r^(3-1) = 18
a . r^2 = 18...... (i)

a . r^(6-1) = 486
a . r^5 = 486 ...... (ii)

dengan membuat perbandingan dari kedua persamaan diperoleh:
r^2/r^5 = 18/486
1/r^3 = 1/27
r^3 = 27
r = akar pangkat 3 dari 27
r = 3

dari persamaan <span>a . r^2 = 18...... (i)
a . 3^2 = 18
a . 9 = 18
a = 18/9 = 2</span>

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