Question

Which of the following sequences are geometric sequences?

Answer 1

Geometric sequence: a ( n ) = a ( n - 1 ) · r
A ) 13 = 10 · r,  r = 1.3
16.9 = 13 · 1.3,  21.97 = 16.9 · 1.3,  28.561 = 21.97 · 1.3,  
37.1293 = 28.561 · 1.3 
C ) 30 = 15 · r,  r = 2, 60 = 30 · 2,  120 = 60 · 2,  240 = 120 · 2 
D ) 0.01 = 0.1 · r,   r = 0.1
0.001 = 0.01 · 0.1 ,   0.0001 = 0.001 · 0.01,  0.00001 = 0.0001 · 0.1
Answer: Geometric sequence are A ), C ) and D ).