Hello,

This time I have come up with a geometric progression problem.

Three natural numbers are known to form a geometric progression. The second member is known to be greater than the first one with +1.

It is required to find the third member of the geometric progression and this is all that is known about it. So, so far I thought up this: let a, b and c be the members. a = b - 1 as said and from the fact that we are dealing with a geometric progression we get:

which is an equation.. with two unknown variables.

To solve it successfully we need a system of equations, i.e. a second equation, which I do not know where to get from, which is my problem.

The answer is c = 4.

I suspect there might be two solutions for b and a, although they are not our concern.

Thank you.