Math Problem Statement

Evaluate the limits: a) lim π‘₯π‘₯β†’1+ 4π‘₯π‘₯βˆ’3 √π‘₯π‘₯ βˆ’1

Solution

We are tasked with evaluating the following limit:

lim⁑xβ†’1+4xβˆ’3xβˆ’1\lim_{{x \to 1^+}} \frac{4x - 3}{\sqrt{x} - 1}

Step 1: Direct Substitution

First, let's check what happens if we directly substitute x=1x = 1:

4(1)βˆ’31βˆ’1=4βˆ’31βˆ’1=10\frac{4(1) - 3}{\sqrt{1} - 1} = \frac{4 - 3}{1 - 1} = \frac{1}{0}

This results in a division by zero, which suggests that the limit may approach infinity, but we need to determine if it's positive or negative infinity, or if it does not exist.

Step 2: Analyze the Behavior for x→1+x \to 1^+

As xβ†’1+x \to 1^+, the numerator 4xβˆ’34x - 3 approaches 11 from the positive side because 4xβˆ’3=4(1+)βˆ’3β‰ˆ14x - 3 = 4(1^+) - 3 \approx 1.

For the denominator xβˆ’1\sqrt{x} - 1, we have x\sqrt{x} approaching 1, but for values slightly greater than 1, x>1\sqrt{x} > 1. Therefore, xβˆ’1\sqrt{x} - 1 will be positive and small.

Thus, for x→1+x \to 1^+, the numerator approaches 1 and the denominator approaches a small positive value. Therefore, the whole fraction grows large and positive.

Step 3: Conclusion

The limit tends towards positive infinity:

lim⁑xβ†’1+4xβˆ’3xβˆ’1=+∞\lim_{{x \to 1^+}} \frac{4x - 3}{\sqrt{x} - 1} = +\infty

Would you like to see more details or have further questions about this solution?

Here are some related questions to explore:

  1. What happens to the limit as xβ†’1βˆ’x \to 1^- instead?
  2. How would you evaluate limits involving higher powers of xx?
  3. Can you apply L'Hopital's rule to this problem?
  4. What would the limit be if the numerator were 4x2βˆ’34x^2 - 3?
  5. How does the concept of one-sided limits differ from general limits?

Tip: When you encounter division by zero in limits, analyze the signs and growth of the numerator and denominator near the point of interest to determine the limit's behavior.

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Math Problem Analysis

Mathematical Concepts

Limits
One-Sided Limits
Infinity in Limits

Formulas

lim x→c f(x)/g(x)
Direct Substitution in Limits

Theorems

Behavior of Functions Near a Point
Limits at Infinity

Suitable Grade Level

Grades 11-12