the question is
Let F(a) be the function which gives the area under the graph of y=x*e^-x between x=0 and x=a for a>0
i found F(a) to be (-x*e^-x)-(e^-x)
then evaluated with the given endpoints i got
(not sure if this is correct)
the second question is
is F increasing or a decreasing function?
is it the same that if the second derivative tells the concavity? pointers anyone?