What is the common ratio of the geometric sequence 7, 28, 112,...?

1 Answer
Sep 19, 2014

The common ratio for this problem is 4.

The common ratio is a factor that when multiplied by the current term results in the next term.

First term: 77

7 * 4 =2874=28

Second term: 2828

28 * 4=112284=112

Third term: 112112

112 * 4=4481124=448

Fourth term: 448448

This geometric sequence can be further described by the equation:

a_n =7*4^(n-1)an=74n1

So if you want to find the 4th term , n=4n=4

a_4=7*4^(4-1)=7*4^(3)=7*64=448a4=7441=743=764=448

Note:

a_n =a_1r^(n-1)an=a1rn1

where a_1a1 is the first term, a_nan is the actual value returned for a specific n^(th)nth term and rr is the common ratio.