th m.g.f. for a geomeric distribuion is pe^t/1-e^tq the first dervative is
(pe^t)(1-e^tq)-(pe^t)(-e^tq)/(1-e^tq)^2 I need the second derivative in order to find v(y) and that is where I am stuck
There is a difference between being stuck because you just don't know what to do, and being stuck because what you have to do is tedious and requires great care. In all honesty I think you're 'stuck' falls into the latter category. You just have to apply the quotient rule and put in all the steps. I think you can do that task just as well as I can - probably better since you will be motivated.
If you genuinely cannot do it, please say so. Preferably, show where abouts in the calculation you were able to get to.