The sum of the first three terms of a geometric sequence is 52. If the third term is changed to 20, then these three terms form an arithmetic sequence.
(a) Find the possible values of the common ration r.
(b) if r2, find the eighth term of the geometric sequence.

Question

The sum of the first three terms of a geometric sequence is 52. If the third term is changed to 20, then these three terms form an arithmetic sequence.
(a) Find the possible values of the common ration r.
(b) if r>2, find the eighth term of the geometric sequence.

rishavraj · Answer

it is like 
a + a(r) + a(r^2) = 52
and 
20 - ar = ar - a

anonymous · Answer

how 20 -a4 = ar -a come

rishavraj · Answer

after replacing the third term from 20... the sequence forms AP.. so the common difference is supposed to be same...

anonymous · Answer

Thanks!