Math Problem Statement

lim (h→0) [f(1+h) - f(1)] / h, where f(x) = 2x^3 - 2

Solution

The problem given is:

limh0f(1+h)f(1)hwheref(x)=2x32\lim_{{h \to 0}} \frac{f(1+h) - f(1)}{h} \quad \text{where} \quad f(x) = 2x^3 - 2

This is the definition of the derivative of f(x)f(x) evaluated at x=1x = 1. We will compute this step by step.

Step 1: Find f(1+h)f(1+h)

Given f(x)=2x32f(x) = 2x^3 - 2, substitute x=1+hx = 1 + h:

f(1+h)=2(1+h)32f(1+h) = 2(1+h)^3 - 2

Now expand (1+h)3(1+h)^3:

(1+h)3=1+3h+3h2+h3(1+h)^3 = 1 + 3h + 3h^2 + h^3

So,

f(1+h)=2(1+3h+3h2+h3)2f(1+h) = 2(1 + 3h + 3h^2 + h^3) - 2 f(1+h)=2+6h+6h2+2h32f(1+h) = 2 + 6h + 6h^2 + 2h^3 - 2 f(1+h)=6h+6h2+2h3f(1+h) = 6h + 6h^2 + 2h^3

Step 2: Find f(1)f(1)

Using f(x)=2x32f(x) = 2x^3 - 2, substitute x=1x = 1:

f(1)=2(1)32=22=0f(1) = 2(1)^3 - 2 = 2 - 2 = 0

Step 3: Substitute into the difference quotient

Now substitute f(1+h)f(1+h) and f(1)f(1) into the expression for the limit:

f(1+h)f(1)h=(6h+6h2+2h3)0h=6h+6h2+2h3h\frac{f(1+h) - f(1)}{h} = \frac{(6h + 6h^2 + 2h^3) - 0}{h} = \frac{6h + 6h^2 + 2h^3}{h}

Simplify the expression:

6h+6h2+2h3h=6+6h+2h2\frac{6h + 6h^2 + 2h^3}{h} = 6 + 6h + 2h^2

Step 4: Take the limit as h0h \to 0

As h0h \to 0:

6+6h+2h266 + 6h + 2h^2 \to 6

Therefore, the value of the limit is:

6\boxed{6}

Let me know if you'd like further details on any of the steps.

Related Questions:

  1. What is the general formula for the derivative using limits?
  2. How do you expand a binomial expression like (1+h)3(1+h)^3?
  3. How would you calculate the derivative for f(x)=2x32f(x) = 2x^3 - 2 directly using differentiation rules?
  4. What are the conditions under which a limit fails to exist?
  5. How can the derivative be interpreted geometrically?

Tip:

When computing limits, it's often helpful to simplify the expression first, especially when dealing with small values like h0h \to 0, as this can make the calculation easier.

Ask a new question for Free

By Image

Drop file here or Click Here to upload

Math Problem Analysis

Mathematical Concepts

Calculus
Limits
Derivatives

Formulas

Limit definition of derivative: lim (h→0) [f(a+h) - f(a)] / h

Theorems

Derivative definition using limits

Suitable Grade Level

Grades 11-12