i am having trouble iwth the following math problem:

lim
x->oo -x/squre root 4+xsquare

I am not sure if i multiple the denominator with the numerator?

The answer depends upon whether the x^2 is in the denominator, and whether you mean sqrt 4 + x^2 or sqrt (4 + x^2). You need to use parentheses to clarify the meaning.

If you mean -x/[sqrt (4 + x^2)]
Then limit as x-> infinity = -1, because the 4 becomes negligible compared to x^2

If x^2 is a separate term, then the limit is infinity