Math Problem Statement

Find the instantaneous rate of change of 𝑓(π‘₯) = π‘₯3 + 1 at π‘₯ = 2 using the first principle

Solution

To find the instantaneous rate of change of the function f(x)=x3+1f(x) = x^3 + 1 at x=2x = 2 using the first principle (also known as the definition of the derivative), we use the following formula:

fβ€²(x)=lim⁑hβ†’0f(x+h)βˆ’f(x)hf'(x) = \lim_{{h \to 0}} \frac{f(x+h) - f(x)}{h}

Step 1: Substitute the function into the formula

Given f(x)=x3+1f(x) = x^3 + 1, we substitute this into the formula for fβ€²(x)f'(x):

fβ€²(x)=lim⁑hβ†’0(x+h)3+1βˆ’(x3+1)hf'(x) = \lim_{{h \to 0}} \frac{(x+h)^3 + 1 - (x^3 + 1)}{h}

Step 2: Simplify the expression

First, expand (x+h)3(x+h)^3:

(x+h)3=x3+3x2h+3xh2+h3(x+h)^3 = x^3 + 3x^2h + 3xh^2 + h^3

Now substitute this back into the expression:

fβ€²(x)=lim⁑hβ†’0x3+3x2h+3xh2+h3+1βˆ’x3βˆ’1hf'(x) = \lim_{{h \to 0}} \frac{x^3 + 3x^2h + 3xh^2 + h^3 + 1 - x^3 - 1}{h}

Simplify the numerator:

fβ€²(x)=lim⁑hβ†’03x2h+3xh2+h3hf'(x) = \lim_{{h \to 0}} \frac{3x^2h + 3xh^2 + h^3}{h}

Factor out hh from the numerator:

fβ€²(x)=lim⁑hβ†’0h(3x2+3xh+h2)hf'(x) = \lim_{{h \to 0}} \frac{h(3x^2 + 3xh + h^2)}{h}

Cancel out the hh in the numerator and denominator:

fβ€²(x)=lim⁑hβ†’0(3x2+3xh+h2)f'(x) = \lim_{{h \to 0}} (3x^2 + 3xh + h^2)

Step 3: Evaluate the limit as hh approaches 0

fβ€²(x)=3x2+3x(0)+02=3x2f'(x) = 3x^2 + 3x(0) + 0^2 = 3x^2

Step 4: Find the derivative at x=2x = 2

Now, substitute x=2x = 2 into the derivative:

fβ€²(2)=3(2)2=3Γ—4=12f'(2) = 3(2)^2 = 3 \times 4 = 12

So, the instantaneous rate of change of f(x)=x3+1f(x) = x^3 + 1 at x=2x = 2 is 1212.

Would you like more details or have any questions?

Here are five related questions to explore further:

  1. How does the instantaneous rate of change compare with the average rate of change between two points?
  2. How would you find the derivative of a more complex function using the first principle?
  3. What is the geometric interpretation of the derivative at a specific point on the graph?
  4. How does the first principle approach differ from using standard derivative rules?
  5. Can you apply the first principle to find the derivative of f(x)=sin⁑(x)f(x) = \sin(x) at a specific point?

Tip: The first principle method is foundational for understanding derivatives and can be applied to any differentiable function, making it essential to grasp before moving on to more advanced derivative rules.

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Math Problem Analysis

Mathematical Concepts

Calculus
Derivatives
First Principle

Formulas

Definition of the derivative

Theorems

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Suitable Grade Level

Grades 11-12