Thread: Hyperbolic maximum turning point

Hi, need a bit of help with this question.

The curve , has a maximum turning point at A, find the x co-ordinates of A in exact logarithmic form.

Differentiated the equation to get , which turns out to be right.

In the answers though, they only have , at first I though this was because you cannot take a natural log of a minus number, but is a positive number.

Any ideas?

Thanks in advance.

I could differentiate it again and then see whether it is a positive or negative number, to determine whether it is a maximum or minimum, but was just wondering if there was an easier method than this.

Also, they have not made any reference to this in the answers :S

Hi Craig -

I haven't done the differentiation, but presumably the other root gives a minimum?

Grandad

Originally Posted by Grandad

Hi Craig -

I haven't done the differentiation, but presumably the other root gives a minimum?

Grandad

Hi Grandad thanks for the reply. That's what I thought, just wondering if there is an obvious way that you just know, something that I'd missed