We are given the integral

We are then asked to explain, intuitively, what happens to the length of the interval (a,b) as a approaches infinity.

Intuitively, the interval is getting shorter and shorter as

*a* goes to infinity. Easy enough, but here's where I'm stuck. We then are asked to mathematically justify this by finding

We are given a hint that is to write either a or b in terms of the other, then write the expression in terms of one variable before taking the limit. Sounds easy, but this is what I've got so far.

Plugging this back in and evaluating the limit is where I get stuck.

**You're subtracting "a^3" rather than "a".**
I'm not really sure how to evaluate this limit.

^^^^^^^^^^^^^^^^^^^^^^^^^

Is there something to be done here by stating that

I don't know where to go with this. Is there some fancy completing the cube action that has to take place to get that a^3 out of the radical?

Even doing

Seems to lead nowhere.

**Shouldn't you be subtracting "a" ?, not it's cube.**
Am I at least on the right track? Or am I completely setting this up wrong?

Who woulda thought I'd be asked to mathematically justify something in a math class. Doh!