Prove $\lim_{a\to 0}\frac{1}{a} = \infty$

1. Oct 15, 2012

operationsres

1. The problem statement, all variables and given/known data

Prove $\lim_{a\to 0^+}\frac{1}{a} = +\infty$ under the $\epsilon[/math] definition of a limit. 2. The attempt at a solution Well, I can't do [itex]\frac{1}{a} - \infty < \epsilon$ can I? Otherwise it's just obvious that it's infinity ..

2. Oct 15, 2012

Zondrina

For this particular problem you need to alter your definition abit since |f(x) - ∞| < ε translates into a useless statement.

You want to use this definition :

$\forall M>0, \exists δ>0 \space | \space 0<|x-c|<δ \Rightarrow f(x) > M$

What this definition essentially means is that we can find a delta such that the function grows without bound.

Start by massaging the expression f(x) > M into a suitable form |x-c| < δ which will give you a δ which MIGHT work.

Then take that δ and show that it implies f(x) > M.