# Math Help - Limits with Infinity

1. ## Limits with Infinity

Use a table of values of f(x) to estimate the value of the limit to four decimal places.

2. Originally Posted by zweevu
Use a table of values of f(x) to estimate the value of the limit to four decimal places.

note that you have (by multiplying by the conjugate over itself):

$\lim_{x \to - \infty} (\sqrt{3x^2 + 9x + 5} - \sqrt{3x^2 + 3x + 2}) \cdot \frac {\sqrt{3x^2 + 9x + 5} + \sqrt{3x^2 + 3x + 2}}{\sqrt{3x^2 + 9x + 5} + \sqrt{3x^2 + 3x + 2}}$

Now what can you do?

3. Since it's to negative infinity, shouldn't there be a negative before the first radical?

4. Originally Posted by zweevu
Since it's to negative infinity, shouldn't there be a negative before the first radical?
no.

what did you get after you simplified the expressions? Hint: you want to factor an $x^2$ out from underneath the square roots in the denominator, and you know what $\sqrt{x^2}$ is, i suppose...