Math Problem Statement

Let \( f(x) \) be a continuous and differentiable function such that \( f(2x) = (e^x + 1) f(x) \forall x \in \mathbb{R} \). Then the value of \( f(0) + f'(0) + f''(0) \) must be?

Solution

Let's go through the problem step by step.

We have:

  1. A continuous and differentiable function f(x)f(x).
  2. Given condition: f(2x)=(ex+1)f(x)xRf(2x) = (e^x + 1) f(x) \quad \forall x \in \mathbb{R}
  3. We need to find the value of f(0)+f(0)+f(0)f(0) + f'(0) + f''(0).

To solve this, let's start by differentiating both sides of the equation.

Step 1: Differentiate with respect to xx

Using the given equation: f(2x)=(ex+1)f(x)f(2x) = (e^x + 1) f(x) we differentiate both sides with respect to xx.

Using the chain rule on the left side: ddxf(2x)=2f(2x)\frac{d}{dx} f(2x) = 2 f'(2x) For the right side: ddx((ex+1)f(x))=exf(x)+(ex+1)f(x)\frac{d}{dx} \left((e^x + 1) f(x)\right) = e^x f(x) + (e^x + 1) f'(x) Thus, we have: 2f(2x)=exf(x)+(ex+1)f(x)2 f'(2x) = e^x f(x) + (e^x + 1) f'(x)

Step 2: Substitute x=0x = 0

Substituting x=0x = 0 into the original equation, we get: f(0)=(e0+1)f(0)f(0)=2f(0)f(0) = (e^0 + 1) f(0) \Rightarrow f(0) = 2f(0) From this, we see that f(0)=0f(0) = 0.

Step 3: Use f(0)=0f(0) = 0 in the Derivatives

Since f(0)=0f(0) = 0, we can use it to find further values of derivatives at x=0x = 0. Based on the given solution (D), we are provided

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Math Problem Analysis

Mathematical Concepts

Differentiation
Functional Equation
Exponential Functions

Formulas

Differentiation rules
Functional equation setup

Theorems

Chain Rule in differentiation

Suitable Grade Level

Undergraduate level (Calculus)