Question

For a G.P if t4=24 t9= 768 find s8

Answer 1

# Answer- S8=765

# Explaination-

# Given-

Considering the geometric progression,

a=?

r=?

t4=24

t9=768

# Solution-

tn=a.r^(n-1)

t4=a.r^3=24

t9=a.r^8=768

t9/t4=768/24=r^8/r^3

r^5=32

r=2

But we know,

t4=a.2^3=24

a=3

Now, Sn=a(1-r^n)/(1-r)

For S8,

S8=3(1-2^8)/(1-2)

S8=3×255

S8=765.

Hope this helps...

Answer 2

Answer:

hope it will help you

S8=765