I'm trying to determine that f(x) = (a/2)*e^(-a|x|) is a pdf for which I have tried to calcuate the integral from -infinity to +infinity but I am no getting a result that converges(even the wolfram alpha widget said the integral doesn't converge). How do I correcly implement this?

I am trying to find the pdf of the inverse of a random variable X, that represents a distribution I defined. I currently have : 

with(Statistics):
T:=Distribution(PDF=(x->piecewise(0<x and x<1,1/4,3<x and x<5,3/8,0)));
X:=RandomVariable(T);
PDF(X,u);
CDF(X,u);
Y:=1/X;
T1:=RandomVariable(Y);

but this seems to be incorrect as I get a message saying T1:=RandomVariable(Y) is being passed a wrong argument. 

What is the right way to obtain the pdf of 1/X?

I've seen a few maple presentations where a block of code is wrapped in a box. Does anyone know how this is done?

What is the right syntax to solve :

min {sum(i=1 to 10) sum(j=1..10) (a_i_j)*(x_i)*(x_j) 

s.t sum(i=1..n) (b_i)*x_i=p and sum(i=1..n)x_i=1 

if a_i_j is a constant, b_i is a constant, p is a constant and x_i, x+j are the decision variables?

I understand that this is a quadratic programming problem and an application of Markowitz optimization. I've tried to use the in-built minimize function but haven't got the right output.

I have a (251*1) vector for which I need to compute the cumulative sum. I'm currently using :

s:=Statistics[CumulativeSum](prices[1..251,1])

defined under the Statistics package but this method doesn't return an output, even though the argument passed is a vector.

Is there another method I can use?