Chapter 2: Problem 50
Compute the average rate of change of the given function over the interval \([x, x+h] .\) Here we assume \([x, x+h]\) is in the domain of the function. \(f(x)=x^{3}\)
Short Answer
Expert verified
The average rate of change of \( f(x)=x^3 \) over \([x, x+h]\) is \( 3x^2 + 3xh + h^2 \).
Step by step solution
01
Understand the Average Rate of Change
The average rate of change for a function between two points is calculated using the formula \( \frac{f(b) - f(a)}{b - a} \), where \( a \) and \( b \) are the endpoints of the interval. In this exercise, \( a = x \) and \( b = x + h \).
02
Calculate Function Values at Endpoints
First, calculate \( f(x) \), which is simply \( x^3 \). Then, calculate \( f(x+h) \) which is \( (x+h)^3 \).
03
Expand \( (x+h)^3 \)
Expand \( (x+h)^3 \) using the binomial theorem: \[ (x+h)^3 = x^3 + 3x^2h + 3xh^2 + h^3 \].
04
Find \( f(x+h) - f(x) \)
Substitute the values from Step 2:\[ f(x+h) - f(x) = (x^3 + 3x^2h + 3xh^2 + h^3) - x^3 \]. Simplify to:\[ 3x^2h + 3xh^2 + h^3 \].
05
Compute the Average Rate of Change
Using the difference from Step 4, the average rate of change is:\[ \frac{3x^2h + 3xh^2 + h^3}{h} \].
06
Simplify the Expression
Factor \( h \) out of the numerator:\[ \frac{h(3x^2 + 3xh + h^2)}{h} \]. Cancel \( h \) from the numerator and denominator to get:\[ 3x^2 + 3xh + h^2 \].
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Binomial Theorem
The binomial theorem is a powerful mathematical tool used to expand expressions of the form \((a + b)^n\) where \(n\) is a non-negative integer. In simpler terms, it tells us how to multiply out powers of a sum.
- It provides a formula that expresses \((a + b)^n\) as a sum involving terms of the form \( \binom{n}{k} a^{n-k}b^k \), where \(k\) is an integer between 0 and \(n\).
- This is incredibly helpful when working with polynomial functions and helps simplify expressions that might otherwise require tedious distribution.
- For example, using the binomial theorem, we can expand \((x+h)^3\) as:\[ (x+h)^3 = x^3 + 3x^2h + 3xh^2 + h^3 \] This expansion is crucial in solving for the average rate of change.
Function Values
Function values are simply the outputs of a function given specific inputs. For each value of the input \(x\), there is a corresponding function value \(f(x)\).
- In polynomial functions like \(f(x) = x^3\), each substitution of \(x\) gives a new value.
- When considering changes over intervals, we evaluate the function at different points to compare results.
- For our average rate of change exercise, we find \(f(x)\) and \(f(x+h)\) by substituting \(x\) and \((x+h)\) into the function.
Interval of a Function
When discussing the interval of a function, we refer to the range of input values over which we evaluate the function. In our example, the interval is \([x, x+h]\).
- An interval gives us a specific path along the function to study.
- Different types of intervals include open intervals such as \((a, b)\), and closed intervals \([a, b]\).
- For functions like \(f(x) = x^3\), we consider intervals to understand how the function behaves within certain boundaries.
Polynomial Functions
Polynomial functions are mathematical expressions involving a sum of powers in one or more variables multiplied by coefficients. They have the general form:\[ P(x) = a_nx^n + a_{n-1}x^{n-1} + \ldots + a_1x + a_0 \]
- Each term's power indicates the degree of the term, with the highest degree term defining the polynomial's degree
- In our function \(f(x) = x^3\), we have a cubic polynomial, which is a polynomial of degree 3.
- Polynomials are smooth and continuous, making them easy to differentiate and analyze, which is why they are frequently used in algebra and calculus.