SOLUTION: Identify the points of discontinuity,holes,vertical asymptotes, and horizontal asmyptotes of each. 1)(x^2+x)/(3x^2-9x) 2)1/x^2-7

Algebra.Com
Question 975202: Identify the points of discontinuity,holes,vertical asymptotes, and horizontal asmyptotes of each.
1)(x^2+x)/(3x^2-9x)
2)1/x^2-7

Answer by Edwin McCravy(20056)   (Show Source): You can put this solution on YOUR website!

I'll just do the first one. 

Factor the numerator and denominator:



Setting the denominator = 0,  3x(x-3) = 0, tells us that
we have discontinuities at x=0, and at x=3

We must decide which type of discontinuity we have at 0 and 3.

1. If we can cancel a common factor in the numerator and denominator
and remove the discontinuity, then it is a "removable discontinuity" 
or "a hole in the graph".

2. If we can't cancel a factor, then the discontinuity is infinite and 
there is an asymptote there.

We have one of each type.

1. We can remove the discontinuity at x=0 by cancelling the x in the 
numerator and denominator.  To find out where the hole is, we cancel
the x and get a new function which is like the original function everywhere
except at the hole.  Let's call it g(x):




g(x) doesn't have a hole at x=0, we substitute and find 
  


So f(x) has a hole at 


2. We cannot remove the discontinuity at x=3 by cancelling, so there is
a vertical asymptote there, a "non-removable" discontinuity.

Since the degree of the numerator and denominator have the same degree, 1,
there is a horizontal asymptote at y = the ratio of the two leading
coefficients, so the horizontal asymptote has equation y=1/3,

So we plot the hole at , the vertical asymptote at x=3, and the horizontal 
asymptote at y=1/3:

 
 



Edwin


RELATED QUESTIONS

I need help with graphing rational funtions. The question is...Identify the points of... (answered by stanbon)
What are the points of discontinuity, holes, vertical asymptotes,x-intercept, and... (answered by stanbon)
Hi heres one more.. For each rational function, identify any holes or horizontal or... (answered by checkley77)
For each rational function, identify any holes or horizontal or vertical asymptotes of... (answered by jim_thompson5910)
For each rational function, identify any holes or horizontal or vertical asymptotes of... (answered by MathLover1)
For each rational function, identify any holes or horizontal or vertical asymptotes of... (answered by stanbon)
List the vertical and horizontal asymptotes of each function, and sketch its graph. (answered by josgarithmetic,Edwin McCravy)
Find all horizontal and vertical asymptotes of the function: f(x) = x/sqrt(x^2-1) (answered by Edwin McCravy,greenestamps)
For each rational function, identify any holes or horizontal or vertical asymptotes of... (answered by stanbon)