Problem 57 - Applied Mathematics: For the Managerial, Life, and Social Sciences

Question

Suppose \(F(x)=f\left(x^{2}+1\right)\). Find \(F^{\prime}(1)\) if \(f^{\prime}(2)=3\).

Step-by-Step Solution

Answer

The derivative of the function F(x) = f(x² + 1) is F'(x) = f'(x² + 1)(2x). Using the given information that f'(2) = 3 and evaluating F'(1), we find that F'(1) = 6.

Step 1: Differentiate F(x) using the Chain Rule

Recall that the Chain Rule states that if we have a composite function F(x) = f(g(x)), then the derivative F'(x) is given by: F'(x) = f'(g(x)) g'(x) In our case, we have F(x) = f(x² + 1). Here, g(x) = x² + 1 and f(u) = f(u) where u = g(x). Now we'll differentiate F(x) using the Chain Rule. F'(x) = f'(g(x)) g'(x) = f'(x² + 1) (2x)

Step 2: Find the value of f'(2)

We're given that f'(2) = 3.

Step 3: Evaluate F'(1)

Now, we'll substitute x = 1 into the derivative F'(x) and use the value of f'(2) to find F'(1). F'(1) = f'(1² + 1) (2×1) = f'(2) × 2 = 3 × 2 = 6 Therefore, F'(1) = 6.

Key Concepts

Derivatives

In calculus, a derivative represents the rate at which a function is changing at any given point. It gives us the 'slope' of the function at that specific location. Derivatives are fundamentally used to find

• Instantaneous rates of change
• Slopes of tangent lines to curves
• Optimize quantities in various applications

When we have a function like \(F(x)=f(x^2+1)\), calculating the derivative \(F'(x)\) involves applying rules special to calculus, such as the chain rule. Derivatives are represented by \(f'(x)\) for the derivative of function \(f(x)\) and provide a powerful tool to analyze the behavior of mathematical models. Using the chain rule allows us to take derivatives of more complex functions with ease.

Composite Functions

Composite functions are essentially functions within functions, denoted as \(f(g(x))\). Here, \(g(x)\) is an inner function nested inside an outer function \(f(x)\). To solve problems involving composite functions, it is necessary to understand both the individual functions and their composition. Let's break it down:

• \(g(x)\): This is the inner function, which is the input to the outer function \(f(x)\).
• \(f(u)\), where \(u = g(x)\): Here \(f(u)\) is the outer function, which takes its input directly from \(g(x)\).

In our example, \(F(x) = f(x^2 + 1)\), the inner function \(g(x)\) is \(x^2 + 1\), which is used as input in \(f(u)\). These composite functions are essential in calculus when dealing with derivatives using the chain rule. It simplifies the process of taking derivatives by breaking them down into manageable parts.

Calculus

Calculus, one of the pillars of mathematics, enables us to understand changes and motion through differentiation and integration. Differentiation, which focuses on derivatives, provides insight into how a quantity changes over time. The chain rule is one of the differentiation techniques used specifically when dealing with composite functions. To see how it works, examine the given function \(F(x) = f(x^2 + 1)\). We apply the chain rule by expressing \(F(x)\) as a composition of two simpler functions and then differentiate:

• Find the derivative of the outer function, here \(f(u)\), with respect to its input \(u\), giving \(f'(u)\).
• Multiply this by the derivative of the inner function \(g(x) = x^2 + 1\), giving \(g'(x) = 2x\).

So, the chain rule simplifies to \(F'(x) = f'(g(x)) \times g'(x)\). In calculus, practicing these steps is crucial as it often comes into play when managing complex functions in mathematics, physics, and engineering.