Math Problem Statement

For the function f(x) = -4x^2 - x - 1, evaluate and fully simplify each of the following: f(x + h), (f(x + h) - f(x)) / h

Solution

The problem asks you to evaluate two expressions for the given function f(x)=4x2x1f(x) = -4x^2 - x - 1.

First Expression: f(x+h)f(x + h)

To find f(x+h)f(x + h), substitute x+hx + h into the function for xx:

f(x+h)=4(x+h)2(x+h)1f(x + h) = -4(x + h)^2 - (x + h) - 1

Now, expand and simplify:

  1. Expand (x+h)2(x + h)^2: (x+h)2=x2+2xh+h2(x + h)^2 = x^2 + 2xh + h^2

  2. Substitute this back into the function: f(x+h)=4(x2+2xh+h2)(x+h)1f(x + h) = -4(x^2 + 2xh + h^2) - (x + h) - 1

  3. Distribute the constants: f(x+h)=4x28xh4h2xh1f(x + h) = -4x^2 - 8xh - 4h^2 - x - h - 1

Thus, the simplified form of f(x+h)f(x + h) is: f(x+h)=4x28xh4h2xh1f(x + h) = -4x^2 - 8xh - 4h^2 - x - h - 1


Second Expression: f(x+h)f(x)h\frac{f(x + h) - f(x)}{h}

Now, use the expressions for f(x+h)f(x + h) and f(x)f(x) to find this difference quotient:

f(x+h)f(x)h=(4x28xh4h2xh1)(4x2x1)h\frac{f(x + h) - f(x)}{h} = \frac{(-4x^2 - 8xh - 4h^2 - x - h - 1) - (-4x^2 - x - 1)}{h}

Simplify the numerator: =(4x28xh4h2xh1)+4x2+x+1= (-4x^2 - 8xh - 4h^2 - x - h - 1) + 4x^2 + x + 1

Cancel the like terms: =(8xh4h2h)= (-8xh - 4h^2 - h)

So, the numerator simplifies to: 8xh4h2h-8xh - 4h^2 - h

Now divide by hh: 8xh4h2hh=8x4h1\frac{-8xh - 4h^2 - h}{h} = -8x - 4h - 1

Thus, the simplified form of the difference quotient is: f(x+h)f(x)h=8x4h1\frac{f(x + h) - f(x)}{h} = -8x - 4h - 1


Would you like more details on any part of the solution or clarification on a step? Here are some related questions you might find useful:

  1. What is the geometric meaning of the difference quotient?
  2. How does this function represent a parabola?
  3. How would the result change if the function had a different degree?
  4. Can you apply this method to a cubic function?
  5. What happens to the difference quotient as hh approaches 0?

Tip: The difference quotient is the foundation for finding the derivative of a function in calculus!

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Math Problem Analysis

Mathematical Concepts

Algebra
Functions
Function Notation
Difference Quotient

Formulas

f(x) = -4x^2 - x - 1
f(x + h) = -4(x + h)^2 - (x + h) - 1
Difference Quotient: (f(x + h) - f(x)) / h

Theorems

Polynomial Expansion
Difference Quotient

Suitable Grade Level

Grades 10-12