Question

The second term in a geometric sequence is 20. The fourth term in the same sequence is 45/4, or 11.25. What is the common ration in this sequence?

Answer 1

second term: 20

third term: 20r

fourth term: (20r)*r = 20r^2

the fourth term is also 11.25, so


20r^2 = 11.25


solve for r

Answer 2

tell me what you get

Answer 3

I got 0.75.

Answer 4

r = 0.75 or r = 3/4

good

Answer 5

now because we have an r^2 term, there's a possibility r could be negative as well

so we have to include r = -3/4

Answer 6

Thank you!

Answer 7

so in the end

r = 3/4 or r = -3/4

Answer 8

yw