# evaluating a limit

• Nov 12th 2009, 05:32 PM
sjara
evaluating a limit
evaluate the limit ..

http://webwork.rutgers.edu/webwork2_...d0abaab3f1.png

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 =(
• Nov 12th 2009, 05:50 PM
skeeter
Quote:

Originally Posted by sjara
evaluate the limit ..

http://webwork.rutgers.edu/webwork2_...d0abaab3f1.png

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 $t \to \infty$
• Nov 12th 2009, 06:00 PM
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
• Nov 12th 2009, 06:01 PM
skeeter
Quote:

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.