Math Problem Statement

Determine the asymptotes of the graph of y = f(x) for the following functions: a) y = \frac{e^x}{x + 1} b) y = x \arccot \frac{2}{x} c) y = (x + 2) e^{1/x} d) y = \sqrt[3]{x^3 + x} e) y = e^x \ln x

Solution

To determine the asymptotes for each function in Exercise 59, let's analyze each given function individually:

a) y=exx+1y = \frac{e^x}{x + 1}

  1. Vertical Asymptote: Vertical asymptotes occur where the denominator equals zero if the numerator does not cancel it out. Here, the denominator x+1=0x=1x + 1 = 0 \Rightarrow x = -1. Thus, there is a vertical asymptote at x=1x = -1.
  2. Horizontal Asymptote: As xx \to \infty, exe^x grows much faster than x+1x+1, so yy \to \infty. Similarly, as xx \to -\infty, ex0e^x \to 0, making y0y \to 0. Thus, there is a horizontal asymptote at y=0y = 0.

b) y=xarccot2xy = x \, \text{arccot} \frac{2}{x}

  1. Vertical Asymptote: For this function, there is no value of xx that makes the argument inside arccot undefined, and thus no vertical asymptote.
  2. Behavior at Infinity: As xx \to \infty, 2x0\frac{2}{x} \to 0 and arccot(0)=π2\text{arccot}(0) = \frac{\pi}{2}, so yxπ2y \approx x \cdot \frac{\pi}{2} \to \infty. Similarly, as xx \to -\infty, 2x0\frac{2}{x} \to 0 and arccot(0)=π2\text{arccot}(0) = \frac{\pi}{2}, so yy \to -\infty. There is no horizontal asymptote, but the behavior indicates that yy grows linearly as xx \to \infty or xx \to -\infty.

c) y=(x+2)e1/xy = (x + 2) e^{1/x}

  1. Vertical Asymptote: No values of xx make this function undefined, so there is no vertical asymptote.
  2. Horizontal Asymptote: As xx \to \infty, 1x0\frac{1}{x} \to 0, so e1/xe0=1e^{1/x} \to e^0 = 1, and yx+2y \approx x + 2, which grows without bound. Similarly, as xx \to -\infty, e1/x1e^{1/x} \to 1, and yx+2y \approx x + 2. Thus, there are no horizontal asymptotes.

d) y=x3+x3y = \sqrt[3]{x^3 + x}

  1. Vertical Asymptote: This function is defined for all xx, so there is no vertical asymptote.
  2. Behavior at Infinity: As xx \to \infty, x3+xx3x^3 + x \approx x^3, so x3+x3x\sqrt[3]{x^3 + x} \approx x. Thus, yy grows without bound as xx \to \infty and xx \to -\infty, indicating no horizontal asymptote.

e) y=exlnxy = e^x \ln x

  1. Vertical Asymptote: This function is defined for x>0x > 0 only (since lnx\ln x is undefined for x0x \leq 0), but it does not exhibit a vertical asymptote; rather, it has a domain restriction at x=0x = 0.
  2. Behavior at Infinity: As xx \to \infty, exlnxe^x \ln x grows exponentially due to exe^x, so there is no horizontal asymptote.

In summary:

  • a) Vertical at x=1x = -1, horizontal at y=0y = 0
  • b) No asymptotes
  • c) No asymptotes
  • d) No asymptotes
  • e) No asymptotes, domain x>0x > 0

Would you like further details on any specific function's asymptotic behavior?

Follow-up Questions:

  1. What are asymptotes and why are they important in graph analysis?
  2. How do you determine vertical asymptotes for more complex functions?
  3. What role does exponential growth play in horizontal asymptotes?
  4. Can logarithmic functions produce horizontal asymptotes, and under what conditions?
  5. How would the asymptotes change if we modified each function slightly?

Tip:

When examining asymptotes, always start by identifying any domain restrictions for vertical asymptotes and evaluating limits at infinity for horizontal ones.

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Math Problem Analysis

Mathematical Concepts

Calculus
Limits
Asymptotes
Exponential Functions
Logarithmic Functions

Formulas

Vertical Asymptote: Set the denominator to zero and solve for x, where applicable.
Horizontal Asymptote: Calculate the limit of f(x) as x approaches infinity and negative infinity.

Theorems

Limit Theorem
Exponential Growth and Decay
Logarithmic Growth

Suitable Grade Level

College Calculus