Hi, I'm having problems with the veru bsics so I cant get any further on my questions. When given a function f(xlt). to find the likelihood you have to do the product of it. I dont understand how the product of sign changes to the summation sign.

For example L(t)= product of( t^x)xe^(-tx)

How do i simplify this to the sum of form?

Im sorry about how its written I dont know how to put in the symbols.