SOLUTION: I am a rational function having a vertical asymptote at the lines x = 3 and x = -3, and a horizontal asymptote at y = 1 . If my only x-intercept is 5, and my y-intercept

Algebra.Com
Question 1185294: I am a rational
function having a vertical asymptote at
the lines x = 3 and x = -3, and a
horizontal asymptote at y = 1 . If my
only x-intercept is 5, and my y-intercept
is - 5/9 , what function am I?

Found 2 solutions by greenestamps, Edwin McCravy:
Answer by greenestamps(13203)   (Show Source): You can put this solution on YOUR website!


The conditions are over-specified; there is no rational function that satisfies all the conditions....

(1) vertical asymptotes at x=3 and x=-3:

This means there must be factor(s) of (x-3) and (x+3) in the denominator; and no other linear factors



(2) horizontal asymptote at y=1:

This means the leading terms of the numerator and denominator are the same (same coefficient and same power). That means the coefficient a is 1, and the number of linear factors is the same in numerator and denominator.



(3) only x-intercept at x=5:

The only factor(s) in the numerator are (x-5). From (2), the total number of linear factors in the numerator and denominator must be the same



(4) y-intercept -5/9:

Set x=0 and see what happens



Ignoring signs, with only factors of 5 in the numerator and only factors of 3 in the denominator, the only way to get a y-intercept of 5/9 is with one factor of 5 in the numerator and two factors of 3 in the denominator. But that would make the function



And that has both the wrong y-intercept (5/9 instead of -5/9) and the wrong horizontal asymptote (y=0 instead of y=1).

ANSWER: There is no rational function with all the prescribed conditions


Answer by Edwin McCravy(20060)   (Show Source): You can put this solution on YOUR website!
Greenestamps didn't think of the sneaky trick of eliminating an x-intercept by
putting an extra factor in the numerator and denominator to create a hole in the
curve instead of having an x-intercept.  I'll use that trick.

To have those vertical asymptotes, the denominator, when set = 0, must have
roots 3 and -3, so the denominator must contain (x-3)(x+3), which has degree 2
and leading coefficient 1.  That might be enough for the denominator.  If so,
the numerator must also be of degree 2 and have leading coefficient 1 in order
to have horizontal asymptote y = 1.  So let's try this version:



To have x-intercept 5, it must go through (5,0).  So we substitute 





Multiply through by 16





To have y-intercept -5/9, it must go through (0,-5/9).  So we substitute 





Multiply both sides by -9



Substituting in






So let's substitute those values for A and B in





Let's graph it and see what we have:



Oh darn! That has an extra x-intercept at (1,0).  Aha, but I can play the trick!
I'll put a hole in the curve at (1,0) by putting in a factor of (x-1) in
the numerator and the denominator:



Then the graph has a hole at (1,0) instead of an x-intercept there.



The un-factored form of the rational function is:



Edwin

RELATED QUESTIONS

I am a rational function having a vertical asymptote at the lines x = 3 and x = -3, and (answered by Edwin McCravy)
I am a rational function having a vertical asymptote at the lines x = 3 and x = -3, and (answered by greenestamps)
I am rational function having a vertical asymptote at the lines x=3 x=-3, and a... (answered by greenestamps)
SOLUTION: I am a rational function having a vertical asymptote at the lines x = 3 and x = (answered by greenestamps)
SOLUTION: I am a rational function having a vertical asymptote at the lines x = 3 and x = (answered by solver91311)
write a rational function that has a vertical asymptote at x=3, a hole at x=-2 and a... (answered by greenestamps)
Write the equation of a rational function that has: - real zeros when x = 1 and 2 - a (answered by Boreal)
Find the equation of a rational function. Vertical Asymptote at x= -6 Horizontal... (answered by greenestamps)
I need to make a rational function with a horizontal asymptote at y=3, vertical asymptote (answered by josgarithmetic,ikleyn)