#F(x) = int xe^(-x) dx#
# = int xd/dx(-e^(-x)) dx#
# = x(-e^(-x)) + int d/dx(x) e^(-x) dx + C#
# = -x e^(-x) + int e^(-x) dx + C#
# = -x e^(-x) - e^(-x) +C#
#\implies F(x) = - e^(-x) (x+1) +C#
#F(0) = 2 implies 2 = - 1 + C#
#\implies F(x) = 3 - e^(-x) (x+1) #