Math Problem Statement

Evaluate the following limits

Evaluate the following limits

Solution

Let's evaluate the limits one by one from the image you provided.

1. Problem (ii):

limx1x1x1\lim_{x \to 1} \frac{x - 1}{\sqrt{x} - 1}

At first glance, if you substitute x=1x = 1, you get a 00\frac{0}{0} indeterminate form. So, let's apply algebraic manipulation to resolve this.

Step 1: Rationalize the denominator

We will multiply both the numerator and denominator by the conjugate of the denominator: x1x1x+1x+1=(x1)(x+1)(x)212\frac{x - 1}{\sqrt{x} - 1} \cdot \frac{\sqrt{x} + 1}{\sqrt{x} + 1} = \frac{(x - 1)(\sqrt{x} + 1)}{(\sqrt{x})^2 - 1^2}

Step 2: Simplify

(x1)(x+1)x1\frac{(x - 1)(\sqrt{x} + 1)}{x - 1} The (x1)(x - 1) cancels out, leaving: limx1x+1\lim_{x \to 1} \sqrt{x} + 1

Step 3: Substitute x=1x = 1

1+1=1+1=2\sqrt{1} + 1 = 1 + 1 = 2

Thus, the value of the limit is: 2\boxed{2}


2. Problem (iii):

limx1(x3)(x+1)x21\lim_{x \to 1} \frac{(x - 3)(x + 1)}{x^2 - 1}

First, substitute x=1x = 1 to check for indeterminate form: (13)(1+1)121=(2)(2)0=40\frac{(1 - 3)(1 + 1)}{1^2 - 1} = \frac{(-2)(2)}{0} = \frac{-4}{0} This is a case of division by zero, so the limit does not exist as a finite number. However, we need to analyze whether it approaches ++\infty or -\infty.

Step 1: Factor the denominator

The denominator x21x^2 - 1 is a difference of squares: x21=(x1)(x+1)x^2 - 1 = (x - 1)(x + 1)

Thus, the expression becomes: (x3)(x+1)(x1)(x+1)\frac{(x - 3)(x + 1)}{(x - 1)(x + 1)}

Step 2: Cancel common factors

The (x+1)(x + 1) terms cancel out: x3x1\frac{x - 3}{x - 1}

Step 3: Substitute x=1x = 1

1311=20\frac{1 - 3}{1 - 1} = \frac{-2}{0}

Step 4: Analyze the sign of the limit near x=1x = 1

  • As x1+x \to 1^+ (from the right), (x1)(x - 1) is positive but very small, so 2small positive number\frac{-2}{\text{small positive number}} \to -\infty.
  • As x1x \to 1^- (from the left), (x1)(x - 1) is negative and very small, so 2small negative number+\frac{-2}{\text{small negative number}} \to +\infty.

Thus, the limit does not exist because the function approaches different infinities from either side: DNE (does not exist)\boxed{\text{DNE (does not exist)}}


Would you like any additional details or further clarification?

Here are some related questions for further practice:

  1. What is the limit of limx0sin(x)x\lim_{x \to 0} \frac{\sin(x)}{x}?
  2. How would you evaluate limx2x24x2\lim_{x \to 2} \frac{x^2 - 4}{x - 2}?
  3. What happens when you apply L'Hopital's Rule to indeterminate forms like 00\frac{0}{0}?
  4. Can you factor x31x^3 - 1 to find the limit as x1x \to 1?
  5. How do you find the one-sided limits as x0x \to 0 for 1x2\frac{1}{x^2}?

Tip: When you encounter indeterminate forms, try algebraic manipulation (like factoring or rationalizing) before applying more advanced techniques like L'Hopital's Rule.

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Math Problem Analysis

Mathematical Concepts

Limits
Algebraic Manipulation
Rationalization
Factorization

Formulas

Limit Formula
Difference of Squares

Theorems

Limit Theorem
Difference of Squares Factorization

Suitable Grade Level

Grades 10-12