How Do You Factor the Numerator of a Rational Function to Find Intercepts?

That means (x-1)(x+2) is a factor and we can use polynomial long division or synthetic division to find the other factor of the polynomial.In summary, the polynomial Y1=(x3+3x2-4)/(x2) has a slant asymptote at y=x+3 and appears to have intercepts at (x-1) and (x+2). To factor the numerator, the rational roots theorem can be used to determine that (x-1) and (x+2) are factors. Using polynomial long division or synthetic division, the other factor can be found.
  • #1
math4life
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Homework Statement


Y1=(x3+3x2-4)/(x2)

Homework Equations


Slant Asymptote at y=x+3. (X-1) and (X+2) appear to be intercepts in the back of the book. How do I factor the numerator to get that?

The Attempt at a Solution


I know this is simple and there is a method to find the zeros of the numerator that I am overlooking- please help.
 
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  • #2


A more systematic method is to apply Rational Roots Theorem. You want to find some binomials that can divide the polynomial numerator and leave no remainder. Try dividing by (X - 1) and see what results. Can you factor this result? OR, try dividing the numerator by (X + 2). How is the result? Remainder?

My guess is you want three linear binomials as a factorization for the numerator, since it has degree of 3. If those other binomials, X-1 and X+2 are factors, then your function would have value of ZERO when X=+1 and when X=-2.
 
  • #3


math4life said:

Homework Statement


Y1=(x3+3x2-4)/(x2)


Homework Equations


Slant Asymptote at y=x+3. (X-1) and (X+2) appear to be intercepts in the back of the book. How do I factor the numerator to get that?


The Attempt at a Solution


I know this is simple and there is a method to find the zeros of the numerator that I am overlooking- please help.
The only integer factors of 4 are (1)(4) and (2)(2). As symbolipoint said, by the "rational roots theorem" the only rational (in this case, integer) roots must be factors of 4: [itex]\pm 1[/itex], [itex]\pm 2[/itex], [itex]\pm 4[/itex]. It easy to try those in the polynomial and see that x= 1 makes it 0: x-1 is a factor. Trying x= -2 also gives a root so x+2 is also a factor.
 

FAQ: How Do You Factor the Numerator of a Rational Function to Find Intercepts?

What is a rational function?

A rational function is a mathematical expression that is written as a ratio of two polynomial functions. It can also be described as a function that can be written in the form f(x) = p(x)/q(x), where p(x) and q(x) are polynomials.

What are the key features of a rational function graph?

The key features of a rational function graph include the horizontal and vertical asymptotes, x and y intercepts, and any holes in the graph. These features can help determine the behavior of the function and its domain and range.

How do you determine the domain and range of a rational function?

To determine the domain and range of a rational function, you need to consider the restrictions on the variable x. The domain is all the possible values of x that make the function valid, while the range is all the possible values of y that the function can output.

How do you find the horizontal and vertical asymptotes of a rational function?

The horizontal asymptote of a rational function can be found by analyzing the degrees of the numerator and denominator polynomials. If the degree of the numerator is less than the degree of the denominator, the horizontal asymptote is y = 0. If the degrees are equal, the horizontal asymptote is the ratio of the leading coefficients. To find the vertical asymptotes, set the denominator equal to zero and solve for x.

How do you sketch a rational function graph?

To sketch a rational function graph, you can start by plotting the key features such as the asymptotes, intercepts, and any known points. Then, use the behavior of the function as x approaches the asymptotes to determine the general shape of the graph. You can also use a table of values to plot additional points and get a more accurate graph.

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