Math Problem Statement

Find the difference quotient of​ f; that​ is, find

StartFraction f left parenthesis x plus h right parenthesis minus f left parenthesis x right parenthesis Over h EndFraction comma

h not equals 0 comma

for the following function. Be sure to simplify.

f left parenthesis x right parenthesis equals x squared minus 5 x plus 7

Solution

The difference quotient of a function f(x)f(x) is given by the formula:

f(x+h)f(x)h,h0\frac{f(x + h) - f(x)}{h}, \quad h \neq 0

For the function f(x)=x25x+7f(x) = x^2 - 5x + 7, follow these steps to find the difference quotient:

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

Substitute x+hx + h into f(x)=x25x+7f(x) = x^2 - 5x + 7:

f(x+h)=(x+h)25(x+h)+7f(x + h) = (x + h)^2 - 5(x + h) + 7

Expand each term:

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

5(x+h)=5x5h-5(x + h) = -5x - 5h

So,

f(x+h)=x2+2xh+h25x5h+7f(x + h) = x^2 + 2xh + h^2 - 5x - 5h + 7

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

Now subtract f(x)=x25x+7f(x) = x^2 - 5x + 7 from f(x+h)f(x + h):

f(x+h)f(x)=(x2+2xh+h25x5h+7)(x25x+7)f(x + h) - f(x) = \left(x^2 + 2xh + h^2 - 5x - 5h + 7\right) - \left(x^2 - 5x + 7\right)

Simplify by canceling out the common terms:

f(x+h)f(x)=2xh+h25hf(x + h) - f(x) = 2xh + h^2 - 5h

Step 3: Divide by hh

Now, divide the expression by hh:

f(x+h)f(x)h=2xh+h25hh\frac{f(x + h) - f(x)}{h} = \frac{2xh + h^2 - 5h}{h}

Simplify the expression by factoring hh out of the numerator:

f(x+h)f(x)h=h(2x+h5)h\frac{f(x + h) - f(x)}{h} = \frac{h(2x + h - 5)}{h}

Since h0h \neq 0, we can cancel out hh:

f(x+h)f(x)h=2x+h5\frac{f(x + h) - f(x)}{h} = 2x + h - 5

Final Answer:

The simplified difference quotient is:

2x+h5\boxed{2x + h - 5}

Do you want more details or have any questions?


Here are 5 related questions to expand on this topic:

  1. How do you find the difference quotient for a cubic function?
  2. What happens to the difference quotient as h0h \to 0?
  3. How is the difference quotient related to the derivative?
  4. How do you compute the difference quotient for a function with a radical expression?
  5. Can you compute the difference quotient for f(x)=3x24x+1f(x) = 3x^2 - 4x + 1?

Tip: The difference quotient is a fundamental concept for understanding the derivative in calculus.

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Math Problem Analysis

Mathematical Concepts

Algebra
Difference Quotient
Quadratic Functions
Limits

Formulas

Difference Quotient Formula: \( \frac{f(x+h) - f(x)}{h} \)

Theorems

Basic Limit Theorem (h ≠ 0)
Quadratic Expansion Theorem

Suitable Grade Level

Grades 10-12