Problem 17 - Calculus and its applications

Question

Differentiate. $$ F(x)=e^{-7 x} $$

Step-by-Step Solution

Answer

The derivative of \( F(x) = e^{-7x} \) is \( F'(x) = -7e^{-7x} \).

Step 1: Identify the Function and Rule

The function we need to differentiate is \( F(x) = e^{-7x} \). Here, \( e^{-7x} \) is an exponential function combined with a linear function. To differentiate \( e^u \) where \( u \) is any function of \( x \), we will employ the chain rule, which states that \( \frac{d}{dx}[e^u] = e^u \cdot u'(x) \).

Step 2: Differentiate the Inner Function

The inner function is \( u(x) = -7x \). Differentiate \( u(x) = -7x \) with respect to \( x \) to get \( u'(x) = -7 \).

Step 3: Apply the Chain Rule

According to the chain rule, \( \frac{d}{dx}[e^{-7x}] = e^{-7x} \cdot (-7) \).

Step 4: Simplify the Expression

Multiplying through by \( -7 \), we have \( -7e^{-7x} \). So, the derivative of the function \( F(x) = e^{-7x} \) is \( F'(x) = -7e^{-7x} \).

Key Concepts

Exponential Functions

Exponential functions are a class of mathematical functions involving the constant base, typically the Euler's number \( e \), raised to a variable power. These are expressed generally as \( f(x) = e^{u(x)} \), where \( u(x) \) can itself be a function of \( x \).

• The base \( e \) is an irrational number approximately equal to 2.71828, and it is key in defining natural exponential functions.
• The exponential part \( e^{u(x)} \) grows (or decays) rapidly depending on the sign and rate of change of \( u(x) \).

The function \( F(x) = e^{-7x} \) is a specific example where \( u(x) = -7x \). Here, the base is \( e \) and the exponent is a linear function of \( x \). This indicates an exponential decay due to \( -7x \) being negative, which causes the function to decrease as \( x \) increases. Understanding the behavior of exponential functions is crucial as they model real-world phenomena like compound interest, population growth, and radioactive decay.

Chain Rule

The chain rule is a fundamental technique in calculus used for differentiating compositions of functions. It allows us to find the derivative of a composite function by dealing with each part separately.

• Suppose you have a composite function \( y = f(g(x)) \). Here, \( f \) is the outer function and \( g \) is the inner function.
• The chain rule gives the derivative as \( y' = f'(g(x)) \cdot g'(x) \).

When differentiating \( F(x) = e^{-7x} \), we note that the outer function is \( e^x \) and the inner function is \( u(x) = -7x \). By the chain rule, the derivative is \( F'(x) = e^{-7x} \cdot (-7) \).
Using the chain rule is an efficient way to handle function compositions, especially when direct differentiation becomes overly complex. Mastery of this rule is essential for tackling more advanced calculus problems effectively.

Calculus

Calculus is the branch of mathematics focused on limits, functions, derivatives, integrals, and infinite series. It provides tools necessary for analyzing and understanding changes and accumulations, making it an essential part of fields such as physics, engineering, and economics.

• Differentiation is the process of finding the derivative, which represents the rate of change of a function with respect to a variable. For example, how \( e^{-7x} \) changes as \( x \) changes.
• In the context of this problem, differentiation was performed using the chain rule to handle the composite function.
• Mastering calculus techniques allows for solving real-world problems, like optimizing functions, modeling phenomena, and understanding dynamic systems.

Calculus not only provides rigorous frameworks for theoretical mathematics but also practical tools for solving diverse problems in various scientific and engineering disciplines.