Solving One-Sided Limit: lim_{x\rightarrow4^{-}} \frac{\sqrt{x}-2}{x-4}

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SUMMARY

The limit lim_{x\rightarrow4^{-}} \frac{\sqrt{x}-2}{x-4} evaluates to 1/4. The initial substitution of values slightly greater than 4 yields an incorrect result of 1 due to the indeterminate form. To resolve this, applying the technique of multiplying by the conjugate, specifically \sqrt{x}+2, simplifies the expression and correctly leads to the limit of 1/4.

PREREQUISITES
  • Understanding of one-sided limits in calculus
  • Familiarity with the concept of indeterminate forms
  • Knowledge of algebraic manipulation techniques, specifically multiplying by the conjugate
  • Basic proficiency in evaluating limits involving square roots
NEXT STEPS
  • Study the method of multiplying by the conjugate in limit problems
  • Explore other techniques for resolving indeterminate forms in calculus
  • Learn about the properties of square root functions in limit evaluations
  • Practice solving various one-sided limits to reinforce understanding
USEFUL FOR

Students studying calculus, particularly those focusing on limits and algebraic techniques for solving them. This discussion is beneficial for anyone looking to enhance their problem-solving skills in mathematical analysis.

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Homework Statement


lim[tex]_{x\rightarrow4^{-}}[/tex] [tex]\frac{\sqrt{x}-2}{x-4}[/tex]


Homework Equations


Typical methods used in solving one-sided limit.


The Attempt at a Solution


I plug in something a little bit bigger than four, like 4.0000001 into x, and I get [tex]\frac{something a little less than zero}{something a little less than zero}[/tex] to equal 1. But the answer is 1/4. How is this so?
 
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Multiply both the top and the bottom by [tex]\sqrt{x}+2[/tex]. This is called "multiplying by the conjugate" and is pretty standard for dealing with limits involving square roots
 

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