Can you take it from here?
Algebraic long division. Or just say . Then the numerator can be split up into 5 times the denominator with a remainder term. It's easier to do it like HallsofIvy suggests; I just prefer to take limits that tend to zero where possible with polynomial limits (for me at least it makes the working clearer).
The general rule of thumb is to take the limit of the highest power of the numerator over the highest power of the denominator. So in your problem:
. The above posts are proving to why that is true.
He kept dividing until he reached a point where you get:
Remember:
If where , then: