Question

For a G.P. T4=120 and T6=480 Find first term and common ratio​

Answer 1

Given that the first term,a=7,

a

n

=ar

n−1

=448 and

S

n

=

r−1

a(r

n

−1)

=889

⇒S

n

=

r−1

ar

n−1

r−a

=889

⇒448r−7=889r−889

⇒882=441r

⇒r=2