Finding the first three terms of a geometric sequence, without the first term or common ratio. 
Given a geometric sequence where the $5$th term $= 162$ and the $8$th term $= -4374$, determine the first three terms of the sequence. 

I am unclear how to do this without being given the first term or the common ratio. please help!!

I had a similar question and tried to solve it alone i used this way 
since the initial value is f(1) so u use this equation f(n) = ar^n-1
since u have f(5) as initial value or actually (known value) then we have to change it to this 
f(n) = a5 * r (n-5)  , so we know that the 8 th term f(8) = -4734 
so :  f(8) = a5 * r(8-5)   and f(5)= 162
-4734 = 162 *r^3
-47324/162 = r^3 
r^3 = -27 then calculate ......
