If a, b, c, d is geometric sequence, then
[tex]\dfrac{b}{a}=\dfrac{c}{b}=\dfrac{d}{c}=const.[/tex]
A. 5; 15; 25; 35
[tex]\dfrac{15}{5}=3;\ \dfrac{25}{15}=\dfrac{5}{3}-NOT[/tex]
B. 5; 10; 20; 40
[tex]\dfrac{10}{5}=2;\ \dfrac{20}{10}=2;\ \dfrac{40}{20}=2-YES[/tex]
C. 6; 12; 18; 24
[tex]\dfrac{12}{6}=2;\ \dfrac{18}{12}=\dfrac{3}{2}-NOT[/tex]
D. 7; 14; 21; 28
[tex]\dfrac{14}{7}=2;\ \dfrac{21}{14}=\dfrac{3}{2}-NOT[/tex]
Answer: The sequence B. 5; 10; 20; 40 is geometric.
