Proving $2- \epsilon < y$ for Limit w/ Epsilon

  • Context: MHB 
  • Thread starter Thread starter Dethrone
  • Start date Start date
  • Tags Tags
    Epsilon Limit
Click For Summary
SUMMARY

The discussion centers on proving the inequality $2 - \epsilon < y$ for the function $y = 2 + \frac{1}{x^2}$ given the condition $x > \frac{1}{(\epsilon)^{1/2}}$, where $\epsilon > 0$. The first part of the proof demonstrates that $y < 2 + \epsilon$ by showing that $x^2 > \frac{1}{\epsilon}$ leads to $\frac{1}{x^2} < \epsilon$. To establish the lower bound, it is noted that for any $x > 0$, $y$ is always greater than 2, thus confirming $y > 2 > 2 - \epsilon$. This provides a complete proof of the desired inequality.

PREREQUISITES
  • Understanding of limits and epsilon-delta definitions in calculus
  • Familiarity with inequalities and algebraic manipulation
  • Basic knowledge of functions and their properties
  • Experience with mathematical proofs and logical reasoning
NEXT STEPS
  • Study the epsilon-delta definition of limits in calculus
  • Explore proofs involving inequalities in mathematical analysis
  • Learn about the behavior of rational functions as variables approach limits
  • Investigate advanced topics in real analysis related to convergence
USEFUL FOR

Students of calculus, mathematics educators, and anyone interested in understanding the formal proofs of limits and inequalities in mathematical analysis.

Dethrone
Messages
716
Reaction score
0
Suppose we are given the function $y=2+\frac{1}{x^2}$. Prove that given $x>\frac{1}{(\epsilon)^{1/2}}$, where $\epsilon > 0$, then $2- \epsilon < y < 2 + \epsilon$.
So the first part is easy:
$$x>\frac{1}{(\epsilon)^{1/2}}$$
$$x^2>\frac{1}{\epsilon}$$
$$\frac{1}{x^2}<\epsilon$$
$$2+\frac{1}{x^2}<2+\epsilon$$

Now, any hints as to how to prove $2-\epsilon < y$? (Wondering)
 
Physics news on Phys.org
Rido12 said:
Suppose we are given the function $y=2+\frac{1}{x^2}$. Prove that given $x>\frac{1}{(\epsilon)^{1/2}}$, where $\epsilon > 0$, then $2- \epsilon < y < 2 + \epsilon$.
So the first part is easy:
$$x>\frac{1}{(\epsilon)^{1/2}}$$
$$x^2>\frac{1}{\epsilon}$$
$$\frac{1}{x^2}<\epsilon$$
$$2+\frac{1}{x^2}<2+\epsilon$$

Now, any hints as to how to prove $2-\epsilon < y$? (Wondering)

For any value of x and for any value of $\varepsilon > 0$ is ...

$\displaystyle y > 2 > 2 - \varepsilon\ (1)$

Kind regards

$\chi$ $\sigma$
 

Similar threads

  • · Replies 5 ·
Replies
5
Views
3K
  • · Replies 16 ·
Replies
16
Views
3K
Replies
2
Views
2K
  • · Replies 10 ·
Replies
10
Views
2K
Replies
4
Views
730
  • · Replies 3 ·
Replies
3
Views
2K
Replies
6
Views
2K
Replies
4
Views
2K
  • · Replies 6 ·
Replies
6
Views
2K
  • · Replies 9 ·
Replies
9
Views
2K