And so you're going to have to have a negative four that comes out. But we don't see a negative four over here. We don't see a negative four here, so we're obviously going to have to divide by a negative four so it cancels out. Another way to think about it is, we could have rewritten this thing. So this is equal to e to the negative four x dx. This is exactly what our problem is, what we need to take the definite integral. And so that it becomes completely clear so that the derivative of this thing is sitting around here.