Why does the integration of a function with a negative lambda result in -1?

[chrismariesan]

okay the problem asks to integrate this function from 0-infinity
i integrated but the answer i get is e^-lambdax from 0 to infinity
so e^0 is 1
and you will have 1-e^-lambda(x) where x is infinity
how does this come out to be -1?
please explain to me...i think i just forgot a rule

 

[daveb]

Hopefully, you're integrating the function f(x) = -lambda*e^(-lambda*x), otherwise your answer is wrong. The integral of this from 0 to infinity is 1. If you are integrating lambda*e^(-lambda*x), then that is -1.

 

[chrismariesan]

ok, i think i figured it out. i was completely ignoring the fact that it was a NEGATIVElambda (x). i realized this shortly after posting.