document.write( "Question 390783: Make up a rational function graph that meets the following conditions:
\n" ); document.write( "a)it will have an oblique asymptote of slope \"not equal\" to 1.
\n" ); document.write( "b)it will have two x-intercepts, one of multiplicity 1 and the other 2.
\n" ); document.write( "c)it will have two vertical asymptotes.
\n" ); document.write( "Then, go through the complete process of graphing your rational function, showing all steps, including the long division.
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Algebra.Com's Answer #277232 by jsmallt9(3758)\"\" \"About 
You can put this solution on YOUR website!
First we'll look at part b. The x-intercepts of a rational function will be where x makes the numerator zero. In order for an x-intercept to exist, (x-r) (where r is the intercept) must be a factor of the numerator. And for one x-intercept to be of multiplicity 2, (x-r) for that intercept must be a factor twice. So if \"r%5B1%5D\" is the x-intercept of multiplicity 1 and \"r%5B2%5D\" is the intercept of multiplicity 2, then the numerator will have the following factors:
\n" ); document.write( "\"%28x-r%5B1%5D%29%28x-r%5B2%5D%29%28x-r%5B2%5D%29\" or \"%28x-r%5B1%5D%29%28x-r%5B2%5D%29%5E2\"

\n" ); document.write( "Next we'll look at part c. For a rational function to have two vertical asymptotes, there must be two numbers that make the denominator zero. If we call these two numbers \"r%5B3%5D\" and \"r%5B4%5D\", then the denominator must have the factors:
\n" ); document.write( "\"%28x-r%5B3%5D%29%28x-r%5B4%5D%29\"

\n" ); document.write( "Last of all we will look at part a. So far our function looks like:
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\n" ); document.write( "I hope it is easy to see that if we were to multiply out the numerator and denominator, the highest power term in the numerator would be \"x%5E3\" and the highest power term in the denominator would be \"x%5E2\". And if we divide \"x%5E3\" by \"x%5E2\" we would get just \"x\". This would give us an oblique asymptote with a slope of 1 (since the coefficient of x is the slope). But we do not want a slope of 1. To get a different slope we need for the coefficients of the highest power terms to be different. One way to get different coefficients would be to add a constant factor to the numerator or denominator that is not a 1. If you add the factor to the numerator then that number will become the slope of the oblique asymptote.

\n" ); document.write( "So our function now looks like:
\n" ); document.write( "
\n" ); document.write( "All we need to do now is pick numbers for \"a\", \"r%5B1%5D\", \"r%5B2%5D\", \"r%5B3%5D\" and \"r%5B4%5D\". In order to get the function you want, pick any number but 1 for \"a\" and make sure that \"r%5B1%5D\", \"r%5B2%5D\", \"r%5B3%5D\" and \"r%5B4%5D\" are all different numbers. As long as you follow the above rules your function will meet all the requirements of the problem no matter what numbers you pick!

\n" ); document.write( "As for the graphing, here are some key ideas:
  • The vertical asymptotes will be \"x+=+r%5B3%5D\" and \"x+=+r%5B4%5D\".
  • The graph will cross the x-axis at \"r%5B1%5D\"
  • The graph will have a relative maximum or minimum at the point (\"r%5B4%5D\", 0). (If you do not know what a \"relative maximum or minimum\" means, then the graph will \"bounce off\" the x-axis at (\"r%5B4%5D\", 0)). (This happens because of the multiplicity of 2.)
  • If x=0 is not a vertical asymptote, then the graph will have a y-intercept. Put a zero in for x and figure out the value of the function when x is zero to determine the y-intercept.
  • To find the equation of the oblique asymptote:
    1. Multiply out both the numerator and the denominator.
    2. Use long division to divide the numerator by the denominator.
    3. You should get something in the form of:
      \n" ); document.write( "ax + b + expression/denominator
      \n" ); document.write( "For large x values the expression/denominator fraction will approach zero. So the oblique asymptote will be the line:
      \n" ); document.write( "y = ax + b
      \n" ); document.write( "where \"a\" is the number you picked earlier and \"b\" is some other number (maybe even the same as \"a\") depending on how the division works out.
  • Two x-intercepts, an oblique asymptote and possibly a y-intercept are not enough to figure out the whole graph. More points are needed. Pick some additional values for x and find the y value for each one. This will give you additional points. Keep finding additional points and plot them until you have a sense as to how the graph goes. Among the x values you try, I would suggest picking x values a little to the left and a little to the right of each of the two vertical asymptotes.
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