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In Exercises 63-66, use the definition of limits at infinity to prove the limit. $$\lim _{x \rightarrow \infty} \frac{1}{x^{2}}=0$$

Short Answer

Expert verified
The limit as x approaches infinity of \(\frac{1}{x^{2}}\) is 0 as proven using the definition of limits at infinity, by showing that for every positive number \(\epsilon > 0\), there is an \(M = \sqrt{1/\epsilon}\) such that for all \(x > M\), the inequality \(|1/x^{2} - 0| < \epsilon\) holds true.

Step by step solution

01

Understand the problem and definition of limits at infinity

The task is to use the definition of limits at infinity to show that \(\lim _{x \rightarrow \infty} \frac{1}{x^{2}}=0\). According to this definition, \(\lim_{x \rightarrow \infty} f(x) = L\) means that for every number \(\epsilon > 0\), there is a corresponding number \(M\) such that whenever \(x > M\), the inequality \(|f(x) - L| < \epsilon\) is true.
02

Apply the definition to the given limit

We want to show that \(\lim _{x \rightarrow \infty} \frac{1}{x^{2}}=0\). By the definition, for each positive number \(\epsilon\), there is some \(M\) such that whenever \(x > M\), it follows that \(|\frac{1}{x^{2}} - 0| < \epsilon\). We need to find such \(M\) that will satisfy this for all \(x > M\).
03

Find the value of M

Looking at the inequality \(|\frac{1}{x^{2}} - 0| < \epsilon\), we see that it simplifies to \(|\frac{1}{x^{2}}| < \epsilon\), and since \(x\) is positive, it further simplifies to \(\frac{1}{x^{2}} < \epsilon\). Rearranging, we get \(x^2 > \frac{1}{\epsilon}\). Taking the square root of both sides, we get \(x > \sqrt{\frac{1}{\epsilon}}\). Therefore, if we let \(M = \sqrt{\frac{1}{\epsilon}}\), we are guaranteed that for all \(x > M\), \(|\frac{1}{x^{2}} - 0| < \epsilon\). This proves that \(\lim _{x \rightarrow \infty} \frac{1}{x^{2}}=0\).

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Key Concepts

These are the key concepts you need to understand to accurately answer the question.

Epsilon-Delta Definition
The epsilon-delta definition is a fundamental concept in calculus, used to rigorously define limits. This definition helps us determine what it means for a function to approach a particular value, called the limit, as the input grows infinitely large. In the context of limits at infinity, we aim to prove \(\lim_{x \rightarrow \infty} f(x) = L\) for a function \(f(x)\). Here's how this works set out:
  • We begin by selecting any positive number \(\epsilon\). This number represents the maximum allowable difference between \(f(x)\) and the limit \(L\).
  • The task is to find a number \(M\), such that for any \(x > M\), the inequality \(|f(x) - L| < \epsilon\) holds true.
This definition ensures that as \(x\) becomes arbitrarily large, the function \(f(x)\) remains arbitrarily close to \(L\). In simple terms, it's a way of describing how a function behaves as its input heads towards infinity.
Limit
In calculus, the concept of a limit describes the value that a function approaches as the input approaches a certain point. Limits help in analyzing the behavior of functions as variables either grow infinitely large or approach a certain value. When working with limits at infinity, the interest is not on a specific point but rather on what happens to the function as the input tends towards infinity. The target is to show that the output, or the function's value, approaches a particular finite number or zero. For example, establishing that \(\lim _{x \rightarrow \infty} \frac{1}{x^2} = 0\) means showing that as \(x\) gets exceedingly large, the value of \(\frac{1}{x^2}\) becomes arbitrarily close to 0. This concept is crucial for understanding the long-term behavior of functions.
Infinite Limits
Infinite limits investigate the behavior of functions as the inputs and outputs reach towards infinity. Unlike finite limits where the goal is to approach a specific number, infinite limits might involve scenarios where either the input or the function's output tends towards infinity.There are two primary scenarios:
  • When \(x\) approaches infinity, we assess whether \(f(x)\) approaches a particular value.
  • Alternatively, when \(f(x)\) itself becomes unbounded, indicating it tends towards infinity or negative infinity.
For instance, by proving that \(\lim _{x \rightarrow \infty} \frac{1}{x^2} = 0\), it shows that for large \(x\), the fraction\(\frac{1}{x^2}\) diminishes towards zero but never becomes infinite. Exploring infinite limits allows us to grasp concepts like end behavior and stability of functions at extreme input values.
Function Behavior
Understanding function behavior is fundamentally about analyzing how a function behaves with changing inputs. Especially when the input becomes exceedingly large. Recognizing function behavior is key when determining limits, especially limits at infinity.Using the function \(f(x) = \frac{1}{x^2}\), the task is to see what happens as \(x\) grows larger and larger. In this case, \(\frac{1}{x^2}\) shows that for growing \(x\), the output becomes smaller, trending towards zero.
  • For enormous values of \(x\), the term \(\frac{1}{x^2}\) reduces rapidly.
  • The function doesn't oscillate, it steadily heads towards zero.
Analyzing this behavior underlines why the limit is zero. Comprehending how functions act at infinity enables predicting their outcomes and interpreting their significance in various mathematical contexts.

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