an=a1.q^(n-1)
a2=4
a1q=4 (1)
S4-a1=28
a1(q+q^2+q^3) =28 (2)
(2)/(1)
(q+q^2+q^3)/q = 7
q^3+q^2-6q=0
q(q^2+q-6)=0
q(q+3)(q-2)=0
q=2
from (1) => a1=2
an=2^n
(an+3)/an
=(2^n+3)/2^n
an=a1.q^(n-1)
a2=4
a1q=4 (1)
S4-a1=28
a1(q+q^2+q^3) =28 (2)
(2)/(1)
(q+q^2+q^3)/q = 7
q^3+q^2-6q=0
q(q^2+q-6)=0
q(q+3)(q-2)=0
q=2
from (1) => a1=2
an=2^n
(an+3)/an
=(2^n+3)/2^n