Limit Problem: Solving \lim_{x \to 2} \frac{\tan (2 - \sqrt{2x})}{x^2 - 2x}

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Homework Help Overview

The discussion revolves around evaluating the limit \(\lim_{x \to 2} \frac{\tan (2 - \sqrt{2x})}{x^2 - 2x}\). Participants explore various approaches to simplify and analyze the limit, focusing on the behavior of the functions involved as \(x\) approaches 2.

Discussion Character

  • Exploratory, Mathematical reasoning, Assumption checking

Approaches and Questions Raised

  • Participants discuss different methods to evaluate the limit, including direct substitution, L'Hôpital's rule, and algebraic manipulation. Some express confusion about the validity of certain limits and the application of trigonometric identities.

Discussion Status

The conversation includes multiple interpretations of the limit, with some participants affirming the correctness of intermediate steps while others question them. There is a mix of agreement and uncertainty regarding the final result, with guidance offered on using L'Hôpital's rule and substitution methods.

Contextual Notes

Some participants highlight the importance of understanding the foundational concepts of limits and derivatives, suggesting that further review may be beneficial for those struggling with the material.

  • #31
ok, the first thing to do in order to determine ##\lim_ {x\rightarrow 0} \frac{\sqrt{x}(x-7)}{\sqrt{x}-\sqrt{7}}## is to substitute the value ##0## in the espression ##\frac{\sqrt{x}(x-7)}{\sqrt{x}-\sqrt{7}}## and see what happen ...
 
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  • #32
##\lim_{x \to 0} \frac{\sqrt{x}(x - 7)}{\sqrt{x} - \sqrt{7}}##
##=\frac{\sqrt{0}(0 - 7)}{\sqrt{0} - \sqrt{7}}##
##=\frac{0 (- 7)}{- \sqrt{7}}##
##= 0##

Then what?
 
  • #33
Then the limit is ##0##
 
  • #34
Ssnow said:
All it is correct but not necessary, I suggest you to put ##x=0## in the original limit, there are indefinite forms as ##\frac{0}{0},\frac{\infty}{\infty}, 0\cdot \infty, \infty-\infty## or not ?
In English these are called indeterminate forms.
 
  • #35
gede said:
How to solve this limit?

\lim_{x \to 0} \frac{\sqrt{x} (x - 7)}{\sqrt{x} - \sqrt{7}}

This is what I get:

\lim_{x \to 0} \frac{\sqrt{x} (x - 7)}{\sqrt{x} - \sqrt{7}} \frac{\sqrt{x} + \sqrt{7}}{\sqrt{x} + \sqrt{7}}
= \lim_{x \to 0} \frac{\sqrt{x} (x - 7) (\sqrt{x} + \sqrt{7})}{(x - 7)}
= \lim_{x \to 0} \sqrt{x}(\sqrt{x} + \sqrt{7})

What is the next solution?
The limit on the first line above can be evaluated merely by substituting x = 0. You don't need to any of the work you show on the following lines.
 
  • #36
Mark44 said:
In English these are called indeterminate forms.

Yes sorry, an error in the translation ...
 

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