The sum of n terms of a G.P is 10-5/2^n-1, find (a) the sum of the first 4 terms (b) the 4th term

Answer 1

I think you mean

Sn = 10 - 5/(2^(n-1)

The first term can be found using n=1, so
a = 10 - 5/2^0 = 5

Now we know that

S2 = 5 + 5r = 10-5/2
r = 1/2

So the sequence is

5, 5/2, 5/4, 5/8, ...

Answer 2

Pls what of the sum of the first four term