Chapter 4: Problem 96
Evaluate. $$\int_{0}^{1}(x+2)^{3} d x$$
Short Answer
Expert verified
16.25
Step by step solution
01
Identify the integral form
The given integral is \(\textstyle \int_{0}^{1}(x+2)^{3} d x \). Since it is a polynomial function within the integrand, it can be integrated by applying the power rule.
02
Expand the polynomial
Before integrating, expand the integrand \((x+2)^{3}\). Using the binomial expansion formula \(a + b\)^3 = a^3 + 3a^2b + 3ab^2 + b^3, the inner term becomes: \((x+2)^{3} = x^3 + 6x^2 + 12x + 8\).
03
Integrate term by term
Now integrate each term of the expanded polynomial separately: \(\textstyle \int_{0}^{1}(x^3 + 6x^2 + 12x + 8) d x\). The integration is performed as follows: \(\textstyle \int_{0}^{1} x^3 dx + \int_{0}^{1} 6x^2 dx + \int_{0}^{1} 12x dx + \int_{0}^{1} 8 dx \).
04
Apply the power rule of integration
Integrate each term using the power rule \( \int x^n dx = \frac{x^{n+1}}{n+1} \): \(\textstyle \int x^3 dx = \frac{x^4}{4}\), \(\textstyle \int 6x^2 dx = 6 \frac{x^3}{3} = 2x^3\), \(\textstyle \int 12x dx = 12 \frac{x^2}{2} = 6x^2\), and \(\textstyle \int 8 dx = 8x\).
05
Evaluate the definite integral
Using the integrated expressions, evaluate them from 0 to 1: \(\left [ \frac{x^4}{4} + 2x^3 + 6x^2 + 8x \right ]_{0}^{1} \). Substitute x = 1 and x = 0: \( \left ( \frac{1^4}{4} + 2(1)^3 + 6(1)^2 + 8(1) \right ) - \left ( \frac{0^4}{4} + 2(0)^3 + 6(0)^2 + 8(0) \right ) \).
06
Simplify and calculate the result
Simplify the expression: \( \left ( \frac{1}{4} + 2 + 6 + 8 \right ) - \left ( 0 \right ) = \frac{1}{4} + 2 + 6 + 8 = 16.25 \).
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Polynomial Integration
Polynomial integration is the process of finding the integral (or antiderivative) of a polynomial function. Here, a polynomial is an expression comprised of variables and coefficients, combined using addition, subtraction, and multiplication. For example, in the integral \( \textstyle \int_{0}^{1}(x+2)^{3} dx \), the expression \( (x+2)^3 \) is initially a polynomial that we need to expand before integrating.
To integrate a polynomial:
To integrate a polynomial:
- Expand the polynomial, if necessary
- Identify the individual terms in the polynomial
- Integrate each term separately using the proper rules
Power Rule
The power rule is a fundamental tool for integrating polynomial functions and states that the integral of \( x^n \), where n is a constant, is given by:
\[ \int x^n dx = \frac{x^{n+1}}{n+1} + C \]
Here, C represents the constant of integration when dealing with indefinite integrals. However, for definite integrals, we do not add C since the bounds essentially cancel out any constants.
For example, if we want to integrate \( x^3 \), using the power rule we get:
\[ \int x^n dx = \frac{x^{n+1}}{n+1} + C \]
Here, C represents the constant of integration when dealing with indefinite integrals. However, for definite integrals, we do not add C since the bounds essentially cancel out any constants.
For example, if we want to integrate \( x^3 \), using the power rule we get:
- Increase the exponent by 1, making it 4
- Divide by the new exponent: \frac{x^4}{4}\
Binomial Expansion
The binomial expansion theorem is a way of expanding expressions that are raised to a power, such as \( (a+b)^n \). This expansion is crucial when dealing with integrals of polynomial expressions raised to a power.
The binomial theorem states:
\[ (a + b)^n = \sum_{k=0}^{n} \binom{n}{k} a^{n-k} b^k \]
Using this, we can expand any binomial into a polynomial. For example, in our specific exercise:
The binomial theorem states:
\[ (a + b)^n = \sum_{k=0}^{n} \binom{n}{k} a^{n-k} b^k \]
Using this, we can expand any binomial into a polynomial. For example, in our specific exercise:
- \