# Math Help - evaluating a limit

1. ## evaluating a limit

evaluate the limit ..

i've tried everything and cant seem to get it.. i multiplied top and bottom by 1/t and squared it all by ^1/2. i got 4 and it was wrong, then i did it another way to get 6/3 and that was wrong too =(

2. Originally Posted by sjara
evaluate the limit ..

i've tried everything and cant seem to get it.. i multiplied top and bottom by 1/t and squared it all by ^1/2. i got 4 and it was wrong, then i did it another way to get 6/3 and that was wrong too =(
$\frac{6t-9}{\sqrt{t^2 + 3t + 5}} = \sqrt{\frac{36t^2-108t+81}{t^2 + 3t + 5}} = \sqrt{\frac{36-\frac{108}{t}+\frac{81}{t^2}}{1 + \frac{3}{t} + \frac{5}{t^2}}}
$

now take the limit as $t \to \infty$

3. it worked thanks! if you dont mind me asking though, why square the top? i thought you only did that when it was to the negative infinity

4. Originally Posted by sjara
it worked thanks! if you dont mind me asking though, why square the top? i thought you only did that when it was to the negative infinity
I squared the numerator to get all of it under the radical.