SOLUTION: I am a rational function having a vertical asymptote at the lines x = 3 and x = -3, and a horizontal asymptote y = 1. If my only x-intercept is 5, and y-intercept is -5/9, What

Algebra ->  Functions -> SOLUTION: I am a rational function having a vertical asymptote at the lines x = 3 and x = -3, and a horizontal asymptote y = 1. If my only x-intercept is 5, and y-intercept is -5/9, What      Log On


   



Question 1045715: I am a rational function having a vertical asymptote at
the lines x = 3 and x = -3, and a horizontal asymptote y = 1.
If my only x-intercept is 5, and y-intercept is -5/9, What
function am I?

Answer by Edwin McCravy(20056) About Me  (Show Source):
You can put this solution on YOUR website!
I am a rational function having a vertical asymptote at
the lines x = 3 and x = -3, and a horizontal asymptote y = 1.
If my only x-intercept is 5, and y-intercept is -5/9, What
function am I?
Since it has vertical asymptotes at the lines x = 3 and x = -3, the
denominator is (x-3)(x+3) or x²-9

Since it has horizontal asymptote y = 1, the leading term of the numerator
must by x²

So it has form:

y%22%22=%22%22%28x%5E2%2BBx%2BC%29%2F%28x%5E2-9%29, for some B and C

Since it has x-intercept 5, it passes through the point (5,0),
so we substitute (x,y) = (5,0)

0%22%22=%22%22%285%5E2%2BB%285%29%2BC%29%2F%28%285%29%5E2-9%29

0%22%22=%22%22%2825%2B5B%2BC%29%2F%2825-9%29

0%22%22=%22%22%2825%2B5B%2BC%29%2F16

Multiply both sides by 16

0%22%22=%22%2225%2B5B%2BC

Since it has y-intercept -5/9, it passes through the point (0,-5/9),
so we substitute (x,y) = (0,-5/9)

-5%2F9%22%22=%22%22%280%5E2%2BB%280%29%2BC%29%2F%280%5E2-9%29

-5%2F9%22%22=%22%22%280%5E2%2BB%280%29%2BC%29%2F%280%5E2-9%29

-5%2F9%22%22=%22%22C%2F%28-9%29

Multiply through by -9

5%22%22=%22%22C

Substitute in

0%22%22=%22%2225%2B5B%2BC

0%22%22=%22%2225%2B5B%2B5

0%22%22=%22%2230%2B5B

-30%22%22=%22%225B

-6%22%22=%22%22B

So 

y%22%22=%22%22%28x%5E2%2BBx%2BC%29%2F%28x%5E2-9%29

becomes


y%22%22=%22%22%28x%5E2-6x%2B5%29%2F%28x%5E2-9%29

Edwin