# Thread: limits of positive/negative infinity question

1. ## limits of positive/negative infinity question

I am having some trouble evaluating two limit questions. They are the same equation but the question asks for an answer for limit of positive infinity and one for limit of negative infinity.

The equation is:

$\sqrt (x^2 + 1)\div (x-1)$

How do I go about solving this question?

Sorry that I didn't right out the limits properly I have lost my syntax sheet for latex and can't find a decent replacement yet

2. Notice that $\dfrac{{\sqrt {x^2 + 1} }}
{{x - 1}} = \dfrac{{\sqrt {1 + \frac{1}
{{x^2 }}} }}
{{1 - \frac{1}
{x}}}$

3. so then when you sub in a very large number the 1/x goes to 0 as it is so close to 0?

4. Originally Posted by smplease
so then when you sub in a very large number the 1/x goes to 0 as it is so close to 0?
Exactly.