SOLUTION: Please help me out with this question: How to find the oblique or curvilinear asymptotes for this function . f(X)= (X^3-1)/(x^2-9) Thanks :)

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Question 892661: Please help me out with this question:
How to find the oblique or curvilinear asymptotes for this function
. f(X)= (X^3-1)/(x^2-9)
Thanks :)

Found 2 solutions by josgarithmetic, Edwin McCravy:
Answer by josgarithmetic(39617)   (Show Source): You can put this solution on YOUR website!
Perform the polynomial division. You should likely find a remainder, which may become increasingly small as x tends to plus or minus infinity, meaning that the quotient without the remainder will be the slant asymptote.

You have a rational expression function. Divide by .
The quotient found is .
Notice the degree of the numerator of the remainder is smaller than the degree of the denominator of the remainder. As x goes to either extreme, the quotient gets closer to , which is the slant asymptote.

Compare with the graph:



,and then showing the included line for the asymptote,

Answer by Edwin McCravy(20054)   (Show Source): You can put this solution on YOUR website!


To find vertical asymptotes, set the denominator = 0



; 
;   

So the two vertical asymptotes are x=-3 and x=3.
We draw those.



Now we ind what you asked for, the oblique or curvilinear 
asymptotes.  To find that we use long division:

                x+0 
x²+0x-9)x³+0x²+0x-1
        x³+0x²-9x
           0x²+9x-1
           0x²+0x+0
               9x-1

and we can rewrite the equation: 





When x gets larger and larger in absolute value
the fraction gets closer and closer to 0, so to 
get the asymptote we drop the fraction and set 
y = the quotient only.

So we have an oblique asymptote, which has 
this equation: 



We draw it:



The we get some points

x|-10| -7 |  -5  |-3.5 |-2.5|
-|---|----|------|-----|-----
y|-11|-8.6|-7.875|-13.5|6.05|


x| 10 | 7  |   5  | 4 | 2.6|
-|----|----|------|---|-----
y|10.9|8.55| 7.75 | 9 |-7.4|

And sketch the graph:



Edwin



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