caraa nomor 14 tolong

Bab Barisan dan Deret
Matematika SMP Kelas IX

Geometri
a + ar = 20
a (1 + r) = 20
1 + r = 20/a

ar² + ar^3 = 45
ar² (1 + r) = 45
1 + r = 45/ar²

20/a = 45/ar²
r² = 45/20
r = √(9/4)
r = 3/2

jawabannya A