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 ratio in this sequence ?

Answer 1

a_1 = ?
a_2 = 20
a_3 = ?
a_4 = 45/4

then you subtract from a_4 the a_2 and the result divide it by 2 you will get the difference betseen two terms
so in this way than you subtract this difference from 20 so will get the first term and than you will add this difference to 20 will get the 3rd term and so will get the right answer to your exercise - hope this will help you

Answer 2

Given: the second term is 20.

Let the common ratio be r.

The 3rd term is the product of the 2nd term and the common ratio. Express this algebraically.

The 4th term is the product of the 3rd term and the common ratio, and is equal to 11.25.

Express this algebraically and solve for the common ratio, r.

Answer 3

Extra credit: Find the first term!