Chapter 3: Problem 68
Find the derivative of \(y\) with respect to the given independent variable. $$y=3^{-x}$$
Short Answer
Expert verified
The derivative is \(-3^{-x} \ln(3)\).
Step by step solution
01
Identify the Problem
We need to find the derivative of the given function, which is expressed as an exponential function: \( y = 3^{-x} \). The goal is to determine \( \frac{dy}{dx} \), the derivative of \( y \) with respect to \( x \).
02
Apply the Exponential Derivative Rule
To find the derivative of an expression of the form \( a^{f(x)} \), use the rule: \( \frac{d}{dx}[a^{f(x)}] = a^{f(x)} \ln(a) \cdot f'(x) \), where \( a \) is a constant. Here, \( a = 3 \) and \( f(x) = -x \).
03
Calculate the Derivative of the Exponent
Find the derivative of \( f(x) = -x \) with respect to \( x \). The derivative, \( f'(x) \), is simply \( -1 \) since the derivative of \( x \) is 1 and we have a negative sign.
04
Substitute into the Derivative Formula
Substitute \( f(x) = -x \), \( f'(x) = -1 \), and \( a = 3 \) into the exponential derivative formula: \[ \frac{dy}{dx} = 3^{-x} \ln(3) \cdot (-1) \].
05
Simplify the Expression
Simplify the expression for the derivative: \[ \frac{dy}{dx} = -3^{-x} \ln(3) \]. This is the simplified expression for the derivative of the given function.
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Exponential Function
An exponential function is a type of mathematical expression where the variable is the exponent. This function takes the form of \( y = a^x \), where \( a \) is a positive constant, known as the base, and \( x \) is the exponent. Exponential functions are widely used in different fields such as finance, biology, and physics because they describe exponential growth or decay.
- For growth, the base \( a \) is greater than 1, indicating that as \( x \) increases, so does \( y \).
- For decay, the base \( a \) is between 0 and 1, meaning that as \( x \) increases, \( y \) decreases.
Exponential Derivative Rule
The exponential derivative rule is a handy tool for finding the derivative of an exponential function. This rule states that if you have a function in the form of \( a^{f(x)} \), its derivative is given by:
This allows us to compute \( \frac{dy}{dx} \) with ease.
- \( \frac{d}{dx}[a^{f(x)}] = a^{f(x)} \ln(a) \cdot f'(x) \)
- \( a^{f(x)} \) stays in the expression, meaning the exponential part remains the same.
- \( \ln(a) \) is the natural logarithm of the base, which is constant for a specific \( a \).
- \( f'(x) \) is the derivative of the exponent \( f(x) \), detailing how \( x \) changes.
This allows us to compute \( \frac{dy}{dx} \) with ease.
Derivative of Exponential Functions
Finding the derivative of an exponential function, particularly one with a negative exponent as given in \( y = 3^{-x} \), involves applying the exponential derivative rule correctly.
\( \frac{dy}{dx} = -3^{-x} \ln(3) \).
This simplified form provides a clear understanding of how the rate of change in \( y \) corresponds to changes in \( x \), while taking into account the base and its natural logarithm.
- The function \( y = 3^{-x} \) maps onto the rule as \( a^{f(x)} = 3^{-x} \).
- The derivative of \( f(x) = -x \) is \( f'(x) = -1 \).
- Substituting these values back into the derivative rule results in:
\( \frac{dy}{dx} = 3^{-x} \ln(3) \cdot (-1) \).
\( \frac{dy}{dx} = -3^{-x} \ln(3) \).
This simplified form provides a clear understanding of how the rate of change in \( y \) corresponds to changes in \( x \), while taking into account the base and its natural logarithm.