Math Problem Statement

difference quotient for f(x)=3x^2-8x+1

Solution

The difference quotient for a function f(x)f(x) is defined as:

f(x+h)f(x)h\frac{f(x+h) - f(x)}{h}

for a small increment hh in xx.

Let's find the difference quotient for f(x)=3x28x+1f(x) = 3x^2 - 8x + 1.

  1. Calculate f(x+h)f(x + h): f(x+h)=3(x+h)28(x+h)+1f(x + h) = 3(x + h)^2 - 8(x + h) + 1

    Expanding (x+h)2(x + h)^2: (x+h)2=x2+2xh+h2(x + h)^2 = x^2 + 2xh + h^2

    So, f(x+h)=3(x2+2xh+h2)8(x+h)+1f(x + h) = 3(x^2 + 2xh + h^2) - 8(x + h) + 1 f(x+h)=3x2+6xh+3h28x8h+1f(x + h) = 3x^2 + 6xh + 3h^2 - 8x - 8h + 1

  2. Subtract f(x)f(x) from f(x+h)f(x + h): f(x+h)f(x)=(3x2+6xh+3h28x8h+1)(3x28x+1)f(x + h) - f(x) = (3x^2 + 6xh + 3h^2 - 8x - 8h + 1) - (3x^2 - 8x + 1) Simplifying by canceling common terms: f(x+h)f(x)=6xh+3h28hf(x + h) - f(x) = 6xh + 3h^2 - 8h

  3. Divide by hh: f(x+h)f(x)h=6xh+3h28hh\frac{f(x + h) - f(x)}{h} = \frac{6xh + 3h^2 - 8h}{h} Simplifying by dividing each term by hh: f(x+h)f(x)h=6x+3h8\frac{f(x + h) - f(x)}{h} = 6x + 3h - 8

So, the difference quotient for f(x)=3x28x+1f(x) = 3x^2 - 8x + 1 is:

f(x+h)f(x)h=6x+3h8\frac{f(x + h) - f(x)}{h} = 6x + 3h - 8

This expression gives the average rate of change of the function over the interval [x,x+h][x, x + h].

Would you like more details on any step or have any questions? Here are some related questions:

  1. How does the difference quotient relate to the derivative of a function?
  2. What happens to the difference quotient as hh approaches zero?
  3. Can you find the derivative of f(x)=3x28x+1f(x) = 3x^2 - 8x + 1 using the limit definition?
  4. How is the difference quotient used in real-world applications?
  5. What is the geometric interpretation of the difference quotient?

Tip: The derivative of a function f(x)f(x) at a point xx is the limit of the difference quotient as hh approaches zero.

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Math Problem Analysis

Mathematical Concepts

Algebra
Difference Quotient
Quadratic Functions
Rates of Change

Formulas

Difference Quotient: (f(x+h) - f(x)) / h
Quadratic Expansion: (x + h)^2 = x^2 + 2xh + h^2

Theorems

Limit Definition of the Derivative
Difference Quotient

Suitable Grade Level

Grades 10-12