Chapter 5: Problem 5
Evaluate the integrals in Exercises \(1-28\). $$\int_{1}^{4}\left(3 x^{2}-\frac{x^{3}}{4}\right) d x$$
Short Answer
Expert verified
The integral evaluates to 47.0625.
Step by step solution
01
Identify the integral to solve
The given integral is \( \int_{1}^{4}\left(3 x^{2}-\frac{x^{3}}{4}\right) d x \). This is an integral of a polynomial function over the interval from \( x=1 \) to \( x=4 \).
02
Apply the Power Rule
To find the antiderivatives of each term, use the power rule: for \( x^n \), the antiderivative is \( \frac{x^{n+1}}{n+1} \).
03
Antidifferentiate Each Term
For \( 3x^2 \), the antiderivative is \( \frac{3x^{3}}{3} = x^3 \). \[\text{For } -\frac{x^3}{4}, \text{ the antiderivative is } -\frac{x^4}{16}. \]
04
Write the Antiderivative Function
Combine the results from Step 3 to write the antiderivative: \[ F(x) = x^3 - \frac{x^4}{16}. \]
05
Evaluate the Definite Integral
Use the Fundamental Theorem of Calculus: evaluate \( F(x) \) at the upper and lower bounds, and subtract: \[ F(4) = 4^3 - \frac{4^4}{16} \]\[ F(1) = 1^3 - \frac{1^4}{16}. \]
06
Calculate the Values
Calculate \( F(4) \): \[ 4^3 - \frac{4^4}{16} = 64 - 16 = 48. \]Calculate \( F(1) \): \[ 1^3 - \frac{1}{16} = 1 - 0.0625 = 0.9375. \]
07
Find the Difference
Subtract to find the value of the definite integral: \[ F(4) - F(1) = 48 - 0.9375 = 47.0625. \]
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Fundamental Theorem of Calculus
The Fundamental Theorem of Calculus is a vital bridge between differentiation and integration. It comes in two parts. First, it tells us that if we integrate a function over an interval, we can find the total change by evaluating its antiderivative at the endpoints of the interval.
Simply put, if you have a function's antiderivative, you can calculate the area under the curve between two points by subtracting the antiderivative's values at these points.
This is expressed as:
Simply put, if you have a function's antiderivative, you can calculate the area under the curve between two points by subtracting the antiderivative's values at these points.
This is expressed as:
- Find an antiderivative of the function.
- Evaluate this antiderivative at the upper limit of the interval.
- Evaluate the antiderivative at the lower limit of the interval.
- Subtract the second result from the first.
Power Rule for Integration
The power rule for integration is a straightforward technique used to find the antiderivatives of polynomial terms. It states that to integrate a term like \( x^n \), you increase the exponent by one and then divide by the new exponent.
This transforms into:
This transforms into:
- If \( x^n \), the antiderivative is \( \frac{x^{n+1}}{n+1} \).
- Always remember to adjust any coefficients, such as in \( 3x^2 \), the process involves \( \frac{3x^{3}}{3} \).
- Don't forget to apply the same rule to any negative or fractional powers.
Polynomial Integration
Polynomial integration is all about applying the fundamental tools of calculus to polynomial expressions. A polynomial is simply a sum of terms like \( ax^n \). During integration:
This simplification makes the daunting task of integration more approachable. Let’s take \(3x^2 - \frac{x^3}{4}\) as an example:
- Each term of the polynomial is treated separately.
- Use the power rule for each term to find their respective antiderivatives.
- Combine these antiderivatives to form a single function.
This simplification makes the daunting task of integration more approachable. Let’s take \(3x^2 - \frac{x^3}{4}\) as an example:
- First, find \(3x^2\)'s antiderivative: \(x^3\).
- Second, integrate \(-\frac{x^3}{4}\): \(-\frac{x^4}{16}\).
- Combine these results to get the total antiderivative of the polynomial.