I'm still trying to grasp the idea of limits as a whole, and infinite limits, individually. I really don't know where to start when it comes to multiplying the numerator and denom by a certain power of 1/x to talk myself through the problem... Here are a few of my homework problems, any addition info to show me how you work through the problem would be greatly appreciated.

1. lim as x approaches infinity of x + x^3 + x^5/1 - x^2 + x^4 =

2. lim as t approaches negative infinity of x^2 + 2/t^3 + t^2 -1

3. lim as x approaches infinity of x + 2/ sq rt (9x^2 + 1)

4. lim as x approaches infinity of [(sq rt(9x^2 + x)) - 3x]

*(9x^2 + x) is the only thing supposed to be under the radical.