Chapter 5: Problem 18
$$\lim _{n \rightarrow \infty} \sum_{i=1}^{n}\left[4-3\left(x_{i}^{*}\right)^{2}+6\left(x_{i}^{*}\right)^{5}\right] \Delta x, \quad[0,2]$$
Short Answer
Expert verified
The value of the limit of the Riemann sum is 64.
Step by step solution
01
Interpret the Exercise as a Riemann Sum
The given expression represents a Riemann sum, which involves taking the limit as the number of subintervals approaches infinity. This Riemann sum approximates the integral of a function over an interval. The sum \(\sum_{i=1}^{n}\left[4-3\left(x_{i}^{*}\right)^{2}+6\left(x_{i}^{*}\right)^{5}\right]\) with \(\Delta x\) indicates the function we are integrating is \(f(x) = 4 - 3x^2 + 6x^5\) over the interval \([0, 2]\).
02
Set Up the Integral
To evaluate the limit of the Riemann sum, set it up as a definite integral. Convert the Riemann sum \(\lim_{n \rightarrow \infty} \sum_{i=1}^{n} f(x_i^*) \Delta x\) to the integral form: \[\int_{0}^{2} (4 - 3x^2 + 6x^5)\, dx.\]
03
Integrate the Function
Now, integrate each term of the function individually:- The integral of \(4\) is \(4x\).- The integral of \(-3x^2\) is \(-x^3\) (as \(-3\times\frac{1}{3}x^3\)).- The integral of \(6x^5\) is \(\frac{6}{6}x^6\) or \(x^6\).Thus, the integral is:\[4x - x^3 + x^6.\]
04
Evaluate the Definite Integral
Evaluate the integral \(4x - x^3 + x^6\) from \(0\) to \(2\):1. Substitute \(2\) into the integrated function: \[ 4(2) - (2)^3 + (2)^6 = 8 - 8 + 64 = 64. \]2. Substitute \(0\) into the integrated function: \[ 4(0) - (0)^3 + (0)^6 = 0. \]3. Take the difference: \[ 64 - 0 = 64. \]
05
Conclusion
Hence, the value of the limit of the Riemann sum, which is the integral of the function over the interval \([0, 2]\), is 64.
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Definite Integral
A definite integral is a key concept in calculus. It allows us to find the exact accumulation of quantities, such as areas under curves or total displacement.
When we talk about the definite integral of a function, we are essentially looking to compute the "net area" under the curve represented by the function from one point to another.
Understanding this provides a deeper grasp of how calculus can be used to measure and calculate continuous changes and accumulations. Furthermore, the area calculated (like in this exercise) can represent various real-world quantities depending on context.
When we talk about the definite integral of a function, we are essentially looking to compute the "net area" under the curve represented by the function from one point to another.
- In the given problem, the function is integrated over the interval from 0 to 2.
- This means we are considering the total impact of the function between these two points.
Understanding this provides a deeper grasp of how calculus can be used to measure and calculate continuous changes and accumulations. Furthermore, the area calculated (like in this exercise) can represent various real-world quantities depending on context.
Function Integration
Function integration involves finding an antiderivative or an integral of a given function. During this process, we determine a new function whose derivative matches the original function.
The step-by-step solution breaks down the integration of each term for the function:
The step-by-step solution breaks down the integration of each term for the function:
- The integral of a constant like 4 results in terms such as 4x, because integrating a constant over a variable adds one to the exponent and divides it by the new exponent.
- For powers of x, such as \(-3x^2\), we add 1 to the exponent and divide by the new power, hence obtaining \(-x^3\).
- Similarly, for \(6x^5\), the process accounts for each term separately, resulting in complete integration as \(x^6\).
Limit Evaluation
Limit evaluation is an integral part of understanding the behavior of functions, particularly as they extend towards infinity.
In the context of our exercise, the limit \(\lim _{n \rightarrow \infty}\) signifies evaluating the sum as the number of terms n approaches infinity, essentially transforming it into the integral. This step is vital because a Riemann sum approximates the integral, becoming the precise value once limits are applied.
In the context of our exercise, the limit \(\lim _{n \rightarrow \infty}\) signifies evaluating the sum as the number of terms n approaches infinity, essentially transforming it into the integral. This step is vital because a Riemann sum approximates the integral, becoming the precise value once limits are applied.
- By calculating the limit of the sum, we transition from an approximation to an exact area or value.
- This concept of limits bridges the gap between discrete and continuous mathematics, showing how sums of many tiny areas (or values) can translate to a well-defined total.