Chapter 3: Problem 26
Find the derivative. \(k(z)=\frac{6}{z^{2}+z-1}\)
Short Answer
Expert verified
The derivative is \( \frac{-12z - 6}{(z^2 + z - 1)^2} \).
Step by step solution
01
Identify the Function Type
The function is a rational function because it involves a polynomial in the numerator and another in the denominator. Specifically, it is of the form \( \frac{a}{g(z)} \) where \( g(z) = z^2 + z - 1 \).
02
Recall the Quotient Rule
To differentiate a quotient \( \frac{f(z)}{g(z)} \), use the quotient rule: \( \left(\frac{f(z)}{g(z)}\right)' = \frac{f'(z)g(z) - f(z)g'(z)}{g(z)^2} \), where \( f(z) = 6 \) and \( g(z) = z^2 + z - 1 \).
03
Differentiate the Numerator and Denominator
Differentiate the numerator \( f(z) = 6 \). Since 6 is a constant, its derivative is 0, \( f'(z) = 0 \). Differentiate the denominator \( g(z) = z^2 + z - 1 \) using the sum rule. Its derivative is \( 2z + 1 \).
04
Apply the Quotient Rule
Substitute the derivatives into the quotient rule formula: \( \left(\frac{6}{z^2 + z - 1}\right)' = \frac{0 \cdot (z^2 + z - 1) - 6 \cdot (2z + 1)}{(z^2 + z - 1)^2} \). Simplify the expression to get \( \frac{-6(2z + 1)}{(z^2 + z - 1)^2} \).
05
Simplify the Expression
Distribute the \( -6 \) in the numerator: \( -6(2z + 1) = -12z - 6 \). Therefore, the derivative is \( \frac{-12z - 6}{(z^2 + z - 1)^2} \).
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Quotient Rule
The Quotient Rule is a formula used in calculus to find the derivative of a division of two functions. If you have a function in the form \(\frac{f(z)}{g(z)}\), the derivative is calculated as \(\left(\frac{f(z)}{g(z)}\right)' = \frac{f'(z)g(z) - f(z)g'(z)}{g(z)^2}\).
- \(f'(z)\) and \(g'(z)\) are the derivatives of the numerator and the denominator, respectively.
- The formula ensures that each component is differentiated separately and then combined.
Rational Functions
Rational functions are fractions where both the numerator and the denominator are polynomials. An example of a rational function is \(k(z) = \frac{6}{z^2 + z - 1}\) as it includes a constant numerator (which can be considered a polynomial of degree 0) and a polynomial denominator.
- They can exhibit a variety of behaviors; they can spike or dip at certain points, or asymptotically approach values as the input grows large.
- The complexity of rational functions often makes them interesting but challenging to differentiate.
Polynomial Derivative
When differentiating polynomials, you apply the power rule to each term individually. The derivative of a term like \(az^n\) is found using \(naz^{n-1}\). This means for each term of the polynomial:
- Increase in powers of \(z\) indicates the number of times the chain rule is applied.
- Coefficients are reduced in line with their variable's power reduction.