How can you show that the limit of this as $\displaystyle t_1$, $\displaystyle t_2$ approaches 0 is not 0...?

$\displaystyle lim_{t \to 0} \left( \frac{t_1 t_2^4}{t_1^2 + t_2^8} \right) $

I understand why it doesn't approach 0 since $\displaystyle t_1^2 + t_2^8 $ approaches 0 quicker than $\displaystyle t_1 t_2^4$, but how can it be shown more formally?

I'd really appreciate the help. Thanks.