Oblique Asymptotes: What happens to the Remainder?

  • Level: Undergrad 
  • Thread starter Thread starter LaMantequilla
  • Start date Start date
  • Tags Tags
    Remainder
Join the discussion
Registration is free. Start your own thread to ask a follow-up.
2 replies · 17K views
LaMantequilla
Messages
8
Reaction score
0
Let's say I'm trying to find the oblique asymptote of the function:

f(x)=
-3x2 + 2
x-1

Forgive my poor formatting.

So because the denominator isn't linear, we do polynomial long division of the function and ultimately get -3x - 3 as our quotient, with a remainder of -1. For the sake of the oblique asymptote, we disregard the remainder. But why? I haven't found a website that explains it; they all simply say to ignore the remainder. It bothers me that we just forget about it, regardless of what it is.
Can you explain to me why we disregard the remainder, and where it "goes?"
 
Physics news on Phys.org
An "asymptote" is a line that a curve approaches as x goes to, in this case, negative infinity and infinity. Yes, long division gives a quotient of -3x- 3 with a remaider of -1. That means that
[tex]\frac{-3x^2+ 2}{x- 1}= -3x- 3- \frac{1}{x- 1}[/tex]
As x goes to either infinity or negative infinity, that last fraction goes to 0.