Let the terms of the GP be α, αr, αr^{2}, αr^{3}

Therefore from the given condition we have

The sum of the first four terms is

The sum of the reciprocal of the first four term is

Dividing (i) by (ii) we get,

Given that the product of the first three terms is 1

Using result (iii) & (iv) we get

α = 2/3

Putting the value of α in (iv) we get,

r = 3/2

From given

**Hence, the value of 2α is 3.**