Chapter 1: Problem 21
(a) Evaluate the function \(f(x)=x^{2}-\left(2^{x} / 1000\right)\) for \(x=1,0.8,0.6,0.4,0.2,0.1,\) and \(0.05,\) and guess the value of \(\lim _{x \rightarrow 0}\left(x^{2}-\frac{2^{x}}{1000}\right)\) (b) Evaluate \(f(x)\) for \(x=0.04,0.02,0.01,0.005,0.003\) and \(0.001 .\) Guess again.
Short Answer
Expert verified
\lim_{x \rightarrow 0}(x^{2} - \frac{2^{x}}{1000}) \approx -0.001.
Step by step solution
01
Evaluate the Function for Given Values of x in Part (a)
We need to evaluate the function \( f(x) = x^2 - \frac{2^x}{1000} \) for the values \( x = 1, 0.8, 0.6, 0.4, 0.2, 0.1, \) and \( 0.05 \). - For \( x = 1 \), \[ f(1) = 1^2 - \frac{2^1}{1000} = 1 - 0.002 = 0.998. \]- For \( x = 0.8 \), \[ f(0.8) = 0.8^2 - \frac{2^{0.8}}{1000} \approx 0.64 - 0.001734 \approx 0.638266. \]- For \( x = 0.6 \), \[ f(0.6) = 0.6^2 - \frac{2^{0.6}}{1000} \approx 0.36 - 0.001515 \approx 0.358485. \]- For \( x = 0.4 \), \[ f(0.4) = 0.4^2 - \frac{2^{0.4}}{1000} \approx 0.16 - 0.001319 \approx 0.158681. \]- For \( x = 0.2 \), \[ f(0.2) = 0.2^2 - \frac{2^{0.2}}{1000} \approx 0.04 - 0.001148 \approx 0.038852. \]- For \( x = 0.1 \), \[ f(0.1) = 0.1^2 - \frac{2^{0.1}}{1000} \approx 0.01 - 0.001072 \approx 0.008928. \]- For \( x = 0.05 \), \[ f(0.05) = 0.05^2 - \frac{2^{0.05}}{1000} \approx 0.0025 - 0.001035 \approx 0.001465. \]
02
Guess the Limit from Part (a) Observations
Based on the computed values of the function as \( x \) approaches zero, we observe that \( f(x) \) approaches a value closer to zero. Therefore, we can guess that: \[ \lim_{x \rightarrow 0}\left(x^{2} - \frac{2^{x}}{1000}\right) \approx 0. \]
03
Evaluate the Function for Additional Values of x in Part (b)
Now evaluate \( f(x) \) for \( x = 0.04, 0.02, 0.01, 0.005, 0.003, \) and \( 0.001 \).- For \( x = 0.04 \), \[ f(0.04) = 0.04^2 - \frac{2^{0.04}}{1000} \approx 0.0016 - 0.001028 \approx 0.000572. \]- For \( x = 0.02 \), \[ f(0.02) = 0.02^2 - \frac{2^{0.02}}{1000} \approx 0.0004 - 0.001014 \approx -0.000614. \]- For \( x = 0.01 \), \[ f(0.01) = 0.01^2 - \frac{2^{0.01}}{1000} \approx 0.0001 - 0.001007 \approx -0.000907. \]- For \( x = 0.005 \), \[ f(0.005) = 0.005^2 - \frac{2^{0.005}}{1000} \approx 0.000025 - 0.001003 \approx -0.000978. \]- For \( x = 0.003 \), \[ f(0.003) = 0.003^2 - \frac{2^{0.003}}{1000} \approx 0.000009 - 0.001002 \approx -0.000993. \]- For \( x = 0.001 \), \[ f(0.001) = 0.001^2 - \frac{2^{0.001}}{1000} \approx 0.000001 - 0.0010007 \approx -0.0009997. \]
04
Guess the Limit from Part (b) Observations
The function \( f(x) \) becomes negative very quickly as \( x \) gets close to zero and approaches a value around \(-0.001\). Therefore, combining both parts, we can refine our guess:\[ \lim_{x \rightarrow 0}\left(x^{2} - \frac{2^{x}}{1000}\right) \approx -0.001. \]
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Function Evaluation
In calculus, evaluating a function involves finding the output of a function for certain inputs. This exercise requires evaluating the function \( f(x) = x^2 - \frac{2^x}{1000} \) at various values of \( x \). When dealing with function evaluation:
- Start by substituting each given input value into the function.
- Simplify the equation as needed, using exponentiation for \( 2^x \) and arithmetic operations to get the final result.
Limit Calculation
Limit calculation is a fundamental concept in calculus representing the value that a function approaches as the input approaches a particular point. The exercise focuses on evaluating the limit as \( x \) approaches 0 for the function \( x^2 - \frac{2^x}{1000} \).Understanding limits involves:
- Observing the trends of the function outputs as \( x \) values get closer to the point of interest.
- Assessing whether the function's output consistently approaches a specific number.
Approximation Techniques
Approximation techniques are often used when the exact solution is inconvenient or impossible to determine. In context, looking at sequences of function values as \( x \) approaches 0 is a form of numerical approximation of the limit.Applying approximation techniques works by:
- Using a sequence of approximations for \( x \) that converge on the limit point.
- Observing the changes in the function value to estimate the limiting behavior.