Recent content by Solitare

Ehild, you've not helped me one bit since we began speaking. Perhaps Ray would be more helpful at this point. I've made my question clear. I've performed the math as I've been taught. I've set the derivative equal to zero, which as we've said countless times now equals -3. I've selected random...

Sorry, Ray. Yes. I meant (2x-5)/(x+3). ehilde, if it's curving at all it's curving upward.

At that point it doesn't, it's fairly constant right there.

To find the value to test for concavity.

Correct. However, deriving to the second derivative and then setting to zero returns x = -3. That'd be the point of inflection, in which case I'd test the numbers around it to determine concavity. But as we've established, that's not defined in the function. Doesn't that mean that there's no...

I'm not sure how this relates to my original question. In my original question I'm lost on whether or not the the function even has a point of inflection since my returned value when I set the second derivative to 0 is x=-3, which we've established isn't defined. Why we're going down this...

It's curved upward, so it's concave upward.

Perhaps I'm not following, but the second derivative of the function that you just posted is 2. There's no way to set that equal to 0.

That there's a change of the sign upon reaching the point of inflection. In the case of concave up, from negative to positive.

Pondering it, could it be as simple as this problem doesn't have a point of inflection; given that (-3+3)^2 returns as zero?

Homework Statement 1. Determine the largest open interval where the function f(x)=2x-5/x+3 is increasing AND concave up (at the same time) Homework Equations The Attempt at a Solution I've run through the problem and arrived at a second derivative of f''(x)= -22/(x+3)^3...