Answer:
r=±0.75
Step-by-step explanation:
Given:
a2= 20
a4= 45/4
As a geometric sequence has a common ratio and is given by:
an=a1(r)^n-1
where
an=nth term
a1=first term
n=number of term
r=common ratio
Now
a2=20=a1(r)^(2-1)
20=a1(r)^1
20=a1*r
Also
a4=45/4=a1(r)^(4-1)
45/4=a1r^3
(a1*r)r^2=45/4
Substituting value of 20=a1*r
(20)r^2=45/4
r^2=45/4(20)
r^2=0.5625
r=±0.75!
