Math Problem Statement

Given the function f(x) = x^2 - 9x - 2, find and simplify the difference quotient f(x+h) - f(x) / h.

Solution

The problem asks to find and simplify the difference quotient f(x+h)f(x)h\frac{f(x+h) - f(x)}{h} for the given function f(x)=x29x2f(x) = x^2 - 9x - 2.

Let's break it down:

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

We need to substitute x+hx + h into the function f(x)f(x).

f(x+h)=(x+h)29(x+h)2f(x + h) = (x + h)^2 - 9(x + h) - 2

Expanding the terms: f(x+h)=(x2+2xh+h2)9(x+h)2f(x + h) = (x^2 + 2xh + h^2) - 9(x + h) - 2 f(x+h)=x2+2xh+h29x9h2f(x + h) = x^2 + 2xh + h^2 - 9x - 9h - 2

Step 2: Compute the difference f(x+h)f(x)f(x + h) - f(x)

Now, subtract f(x)f(x) from f(x+h)f(x + h):

f(x+h)f(x)=(x2+2xh+h29x9h2)(x29x2)f(x + h) - f(x) = \left(x^2 + 2xh + h^2 - 9x - 9h - 2\right) - \left(x^2 - 9x - 2\right) Distribute the negative sign and simplify: f(x+h)f(x)=x2+2xh+h29x9h2x2+9x+2f(x + h) - f(x) = x^2 + 2xh + h^2 - 9x - 9h - 2 - x^2 + 9x + 2 Cancel out the common terms x2x^2, 9x-9x, and 2-2: f(x+h)f(x)=2xh+h29hf(x + h) - f(x) = 2xh + h^2 - 9h

Step 3: Simplify the difference quotient

Now, divide by hh:

f(x+h)f(x)h=2xh+h29hh\frac{f(x + h) - f(x)}{h} = \frac{2xh + h^2 - 9h}{h}

Factor out hh from the numerator: f(x+h)f(x)h=h(2x+h9)h\frac{f(x + h) - f(x)}{h} = \frac{h(2x + h - 9)}{h}

Cancel hh from the numerator and denominator (assuming h0h \neq 0): f(x+h)f(x)h=2x+h9\frac{f(x + h) - f(x)}{h} = 2x + h - 9

Answer:

The simplified form of the difference quotient is: 2x+h92x + h - 9

This matches the last option in the multiple-choice list, so the correct answer is 2x + h - 9.

Would you like further details or have any questions?

Here are 5 related questions to explore:

  1. How does the difference quotient relate to the derivative of a function?
  2. What happens to the difference quotient as hh approaches 0?
  3. Can you compute the derivative of f(x)f(x) directly using the power rule?
  4. What is the geometric interpretation of the difference quotient?
  5. How does this problem change if the function was cubic instead of quadratic?

Tip: The difference quotient is foundational in calculus, leading to the concept of the derivative, which gives the slope of the tangent line to the curve at any point.

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Math Problem Analysis

Mathematical Concepts

Calculus
Difference Quotient
Limits
Quadratic Functions

Formulas

f(x + h) = (x + h)^2 - 9(x + h) - 2
f(x + h) - f(x)
(f(x + h) - f(x)) / h

Theorems

Difference Quotient Theorem
Quadratic Expansion

Suitable Grade Level

Grades 10-12, Calculus 1