Chapter 2: Problem 38
Find the horizontal asymptote, if there is one, of the graph of each rational function. $$f(x)=\frac{15 x}{3 x^{2}+1}$$
Short Answer
Expert verified
The horizontal asymptote of the function \(f(x)=\frac{15x}{3x^{2}+1}\) is \(y=0\).
Step by step solution
01
Identify the order of the numerator and the denominator
The order (or degree) of the numerator of the given function \(f(x)=\frac{15x}{3x^{2}+1}\) is 1 and the order of the denominator is 2. When the order of the denominator is greater than the numerator, the horizontal asymptote is at \(y=0\)
02
Determine the limit as x approaches infinity
To determine the limit as x approaches infinity, one needs to divide the numerator and the denominator by \(x^{2}\) (since 2 is the highest order of the denominator or numerator). After that, we determine the limit: \[ \lim_{x\to\infty} \frac{(15/x)}{(3+1/x^{2})}\]Since \(15/x\) and \(1/x^{2}\) tends to 0 when x tends to infinity, the limit of the function as x approaches infinity is zero.
03
Identify the horizontal asymptote
The value of the function as x approaches infinity is zero, so the line \(y=0\) is the horizontal asymptote of the function.
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Rational Functions
A rational function is a type of function that can be defined as the ratio of two polynomials. This means it can be expressed in the form \( f(x) = \frac{P(x)}{Q(x)} \) where \( P(x) \) and \( Q(x) \) are polynomials, and \( Q(x) eq 0 \). Understanding rational functions involves recognizing both their algebraic structure and how they behave graphically.
- They are characterized by polynomial expressions in both the numerator \( P(x) \) and the denominator \( Q(x) \).
- The domain of these functions is restricted by the zeros of the denominator, as division by zero is undefined.
- Common features of rational functions include vertical asymptotes, horizontal asymptotes, and removable discontinuities.
Degrees of Polynomials
The degree of a polynomial is a critical concept in understanding the behavior of polynomials in rational functions. It refers to the highest power of \( x \) in a polynomial and gives us insight into the end behavior of the function.
- The degree helps in determining the leading term, which significantly influences the graph's shape as \( x \) moves towards infinity.
- For the polynomial \( P(x) = a_nx^n + a_{n-1}x^{n-1} + \ldots + a_0 \), the degree is \( n \).
- If the degree of the numerator is less than the degree of the denominator, the horizontal asymptote is \( y = 0 \).
- If both have the same degree, the horizontal asymptote is given by the ratio of the leading coefficients.
- If the degree of the numerator is greater than that of the denominator, there is no horizontal asymptote.
Limits at Infinity
Limits help in understanding the behavior of a function as the input \( x \) becomes very large (positively or negatively). In rational functions, limits at infinity play a crucial role in finding horizontal asymptotes.
- The focus is on determining \( \lim_{x\to\infty} f(x) \), which is critical when looking for horizontal asymptotes.
- Evaluating limits at infinity often involves simplifying the rational function by dividing each term by \( x^n \), where \( n \) is the highest degree present in either the numerator or denominator.
- Ultimately, these limits indicate the horizontal line that the graph of the function approaches but never actually reaches or crosses.