Question

Dng menggunakan deret geometri. suku pertama 100 n jlh 3 suku pertama 175,maka suku ke 4 adalah...

Answer 1

a = 100
S3 = 175
U4 = ?

cara dilampiran ^_^

Answer 2

A = 100
a + ar + ar² = 175
100 + 100r + 100r² = 175
100r² + 100r - 75 = 0
4r² + 4r - 3 = 0
(2r - 1)(2r + 3) = 0
r = 1/2 --> U₄ = ar³ = 100(1/8) = 12,5
r = -3/2 --> U₄ = 100(-27/8) = -337,5