# How do you write a rule for the nth term of the geometric sequence and then find #a_5# given #a_4=-3, r=-2#?

##### 1 Answer

Sep 10, 2017

#### Explanation:

#"the terms in a standard geometric sequence are"#

#a,ar,ar^2,ar^3, ...... , ar^(n-1)#

#"where a is the first term and r the common ratio"#

#"the nth term is "#

#•color(white)(x)a_n=ar^(n-1)#

#a_4=ar^3=-3rArra=(-3)/(-2)^3=(-3)/(-8)=3/8#

#rArra_n=3/8(-2)^(n-1)#

#rArra_5=3/8(-2)^4=3/8xx16=6#