I have a random variable problem. I need to prove that my equation I came up with is a valid probability mass function. In the problem, I came up with this for my probability mass function: [tex]\Sigma[/tex] [tex]12/(k+4)(k+3)(k+2)[/tex] Maple says that this does in fact converge to 1, so it's valid; however...I can't use "Maple said so" as an answer. My attempt was to break it up using partial fraction decomposition: ([tex]6/(k+4)[/tex]) - ([tex]12/(k+3)[/tex]) + ([tex]6/(k+2)[/tex]) I was hoping that this would be telescoping, but it is not. Does anyone have an idea on how I can prove that this converges to 1?