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a. Calculate the derivative of the given function without using either the product or quotient rule. b. Use the product or quotient rule to find the derivative. Check that you obtain the same answer. HINT [See Quick Examples on page 810.] \(r(x)=100 x^{2.1}\)

Short Answer

Expert verified
The derivative of the function \(r(x) = 100x^{2.1}\) is \(r'(x) = 210x^{1.1}\), and this is confirmed by calculating the derivative using both methods - without the product or quotient rule and using the product rule.

Step by step solution

01

To find the derivative of \(r(x)\) without using the product or quotient rule, we can just apply the power rule. Recall the power rule states that if \(f(x) = x^n\), then \(f'(x) = nx^{n-1}\). Using the power rule, we can differentiate the given function: \[r'(x) = \frac{d(100x^{2.1})}{dx} = 100 \cdot \frac{d(x^{2.1})}{dx}\] #Step 2: Apply the power rule#

Now we will apply the power rule to the remaining part: \[r'(x) = 100 \cdot 2.1x^{2.1-1} = 100(2.1x^{1.1}) = 210x^{1.1}\] So, the derivative without using product or quotient rule is \(r'(x) = 210x^{1.1}\). #Step 3: Differentiate using product or quotient rule#
02

Now, let's find the derivative of \(r(x)\) using the product rule. First, write the given function as a product of two functions, say \(u(x) = 100\) and \(v(x) = x^{2.1}\). Product rule states that \((uv)' = u'v + uv'\). So, we need to find the derivatives of \(u(x)\) and \(v(x)\), and then apply the product rule. #Step 4: Differentiate u(x) and v(x)#

To differentiate u(x): \[u'(x) = \frac{d(100)}{dx} = 0\] To differentiate v(x), we use the power rule: \[v'(x) = \frac{d(x^{2.1})}{dx} = 2.1x^{2.1-1} = 2.1x^{1.1}\] #Step 5: Apply the product rule#
03

Now we will apply the product rule: \[(uv)' = u'v + uv' = 0 \cdot x^{2.1} + 100 \cdot 2.1x^{1.1} = 0 + 210x^{1.1}\] Therefore, using the product rule, we get the derivative as \(r'(x) = 210x^{1.1}\). #Step 6: Compare the results#

Now, we can compare the derivatives found in Steps 2 and 5: Derivative without using product or quotient rule: \(r'(x) = 210x^{1.1}\) Derivative using product rule: \(r'(x) = 210x^{1.1}\) Both methods yield the same derivative, so we can conclude that our answer is correct. The derivative of the function \(r(x) = 100x^{2.1}\) is \(r'(x) = 210x^{1.1}\).

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Key Concepts

These are the key concepts you need to understand to accurately answer the question.

Derivative Calculation
Calculating derivatives is a fundamental part of calculus, which helps us understand how a function changes through its rate of change. In simple terms, the derivative of a function represents the slope of the tangent line to the function at any point. For any given function, the derivative calculation involves some specific rules and steps that simplify the process.

When tasked with finding the derivative of a polynomial function, you encounter a set of rules, such as the power rule or the product rule, which are essential tools in differentiation. By understanding and applying these rules, one can efficiently determine the derivatives of various functions, whether it’s a simple monomial or a complicated product of multiple terms. This makes derivative calculations not only manageable but straightforward once these rules are mastered.
Power Rule
The power rule is one of the most straight-forward rules in calculus differentiation and is crucial for finding derivatives of functions in the form of a single term raised to a power. The rule states that if you have a function: - \( f(x) = x^n \), then the derivative of this function is - \( f'(x) = n imes x^{n-1} \).

The power rule simplifies the differentiation process significantly, as instead of expanding power expressions, we just multiply the power by the coefficient and decrease the power by one. For instance, when you have a function like \( r(x) = 100x^{2.1} \), applying the power rule directly gives:
  • Multiply the exponent with the coefficient: \( 2.1 \times 100 = 210 \)
  • Decrease the exponent by 1: \( 2.1 - 1 = 1.1 \)
Hence, the derivative becomes \( r'(x) = 210x^{1.1} \). The power rule's simplicity helps in quickly working through derivatives and is applicable whenever you encounter polynomials or similar function forms.
Product Rule
The product rule is another critical component of calculus differentiation when dealing with products of two functions. It is necessary when you have two differentiable functions multiplied together. The product rule states:
  • Given two functions \( u(x) \) and \( v(x) \), the derivative of their product \( uv \) is: \((uv)' = u'v + uv'\)


In the context of our function \( r(x) = 100x^{2.1} \), if you consider \( u(x) = 100 \) (a constant) and \( v(x) = x^{2.1} \), application of the product rule involves:
  • Finding \( u'(x) \), the derivative of 100, which is 0, since it's a constant.
  • Calculating \( v'(x) \) using the power rule: \( 2.1x^{1.1} \)
  • Combining these using the product rule: \( uv' = 100 \times 2.1x^{1.1} = 210x^{1.1} \)
Thus, applying the product rule also yields \( r'(x) = 210x^{1.1} \). This not only reaffirms our results from the power rule but also illustrates that the product rule’s utility shines when separating out terms into different functions, particularly when you're faced with intricate combinations of differentiable expressions.

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