Problem 32 - College Algebra with Modeling and Visualization

Question

Find any horizontal or vertical asymptotes. $$ f(x)=\frac{2 x^{2}-3 x+1}{2 x-1} $$

Step-by-Step Solution

Answer

Vertical asymptote at \( x = \frac{1}{2} \); no horizontal asymptote.

Step 1: Identify Potential Horizontal Asymptotes

To find horizontal asymptotes of a rational function \( y = \frac{P(x)}{Q(x)} \), compare the degrees of the numerator \( P(x) \) and the denominator \( Q(x) \).Here, the degree of the numerator \( 2x^2 - 3x + 1 \) is 2 and the degree of the denominator \( 2x - 1 \) is 1. Since the degree of the numerator is greater than the degree of the denominator, there are no horizontal asymptotes.

Step 2: Find Vertical Asymptotes

Vertical asymptotes occur at values of \( x \) that make \( Q(x) = 0 \), provided \( P(x) \) at those \( x \) values is not zero.Set \( 2x - 1 = 0 \) and solve for \( x \):\[2x - 1 = 0 \]\[2x = 1 \]\[x = \frac{1}{2} \]Since \( x = \frac{1}{2} \) does not make the numerator zero, \( x = \frac{1}{2} \) is a vertical asymptote.

Key Concepts

Horizontal Asymptotes

Horizontal asymptotes describe how a function behaves as the input, usually denoted as \( x \), approaches positive or negative infinity. For rational functions, determining horizontal asymptotes involves comparing the highest power of \( x \) in the numerator and the denominator. If the degree of the numerator \( P(x) \) is less than the degree of the denominator \( Q(x) \), the horizontal asymptote is always \( y = 0 \).
If both degrees are equal, the horizontal asymptote is the ratio of the leading coefficients of \( P(x) \) and \( Q(x) \).
However, if the degree of the numerator is greater, like in our exercise where the numerator \( 2x^2 - 3x + 1 \) is of degree 2 and the denominator \( 2x - 1 \) is of degree 1, there are no horizontal asymptotes. The behavior of the function at infinity is influenced by the polynomial's leading term and can direct us to oblique asymptotes, not horizontal ones.

Vertical Asymptotes

Vertical asymptotes occur when a function approaches a specific value along the x-axis, causing the output \( f(x) \) to head towards positive or negative infinity. For rational functions, this usually happens when the denominator \( Q(x) \) equals zero. However, for an asymptote to exist at \( x = a \), \( P(a) \) must not be zero; otherwise, you'd have a hole instead of an asymptote.
To find vertical asymptotes, solve \( Q(x) = 0 \). In our example, we set \( 2x - 1 = 0 \) and solve for \( x \):

• \( 2x - 1 = 0 \)
• \( 2x = 1 \)
• \( x = \frac{1}{2} \)

This value indicates where the vertical asymptote occurs, as it does not make the numerator zero. Therefore, the vertical asymptote is at \( x = \frac{1}{2} \). Note that vertical asymptotes give us information about the infinite behavior of the graph near these points.

Rational Functions

Rational functions are expressions of the form \( \frac{P(x)}{Q(x)} \), where both \( P(x) \) and \( Q(x) \) are polynomials, and \( Q(x) \) is not zero. Studying their asymptotes help us understand the function's long-term behavior and crucial points where the graph may shift drastically.

• The domain of rational functions excludes values that make the denominator zero, which lead to vertical asymptotes or holes in the graph, depending on the behavior of the numerator at these points.
• Horizontal or sometimes oblique asymptotes reveal the end behavior of these functions, which is what happens as \( x \) approaches infinity or negative infinity.

In practical applications, rational functions model phenomena where rates of change are significant, such as in physics and economics. When analyzing such functions, recognizing asymptotic behavior provides insights into limits and continuity.