Math Problem Statement

Graph the function f(x) = (x^2 - 1) / (x - 1) and find lim(x→1) f(x). Use your graph to help find the limit and discuss whether the limit exists.

Solution

The function given is:

f(x)=x21x1f(x) = \frac{x^2 - 1}{x - 1}

Step 1: Simplify the Function

Notice that x21x^2 - 1 is a difference of squares, which can be factored as:

x21=(x1)(x+1)x^2 - 1 = (x - 1)(x + 1)

So the function becomes:

f(x)=(x1)(x+1)x1f(x) = \frac{(x - 1)(x + 1)}{x - 1}

For x1x \neq 1, we can cancel the common term (x1)(x - 1), which simplifies the function to:

f(x)=x+1forx1f(x) = x + 1 \quad \text{for} \quad x \neq 1

Step 2: Analyze the Limit

Now, we need to find the limit:

limx1f(x)\lim_{x \to 1} f(x)

Since the simplified function is f(x)=x+1f(x) = x + 1 for x1x \neq 1, we can directly substitute x=1x = 1 into the simplified function:

limx1(x+1)=1+1=2\lim_{x \to 1} (x + 1) = 1 + 1 = 2

Thus, the limit exists and is:

limx1f(x)=2\lim_{x \to 1} f(x) = 2

Step 3: Behavior at x=1x = 1

Even though the limit as x1x \to 1 exists, the function is undefined exactly at x=1x = 1 because the original function has the term 00\frac{0}{0} at this point, which is indeterminate. Thus, there is a hole in the graph at x=1x = 1.

Step 4: Graph of the Function

  • For x1x \neq 1, the function behaves like a straight line f(x)=x+1f(x) = x + 1.
  • At x=1x = 1, there is a hole in the graph.

The graph will be a straight line with a slope of 1 and a y-intercept at (0,1)(0, 1), but with a hole at the point (1,2)(1, 2).

Summary

  • The limit limx1f(x)=2\lim_{x \to 1} f(x) = 2 exists.
  • The function is undefined at x=1x = 1, so there is a hole in the graph at (1,2)(1, 2).

Would you like a detailed graph or further clarification on any part?


Here are 5 related questions:

  1. What happens to the limit of a function if the denominator does not factor cleanly?
  2. How do you handle limits when a function gives a 00\frac{0}{0} indeterminate form?
  3. Can limits exist if a function is undefined at a point?
  4. How does factoring help in simplifying rational functions for limits?
  5. What is the difference between one-sided and two-sided limits?

Tip: Always check for factoring opportunities when simplifying functions to resolve indeterminate forms.

Ask a new question for Free

By Image

Drop file here or Click Here to upload

Math Problem Analysis

Mathematical Concepts

Limits
Factorization
Indeterminate Forms

Formulas

f(x) = (x^2 - 1) / (x - 1)
Difference of squares: x^2 - 1 = (x - 1)(x + 1)
Limit definition: lim(x→c) f(x)

Theorems

Limit Laws
Factoring to resolve indeterminate forms

Suitable Grade Level

Grades 10-12 (High School Calculus)