Math Problem Statement

Find and simplify the difference quotient for f(x) = -x^2 + 7x + 4 using f(x+h) - f(x)/h.

Solution

The problem in the image asks to find and simplify the difference quotient for the given function:

f(x)=x2+7x+4f(x) = -x^2 + 7x + 4

The difference quotient formula is:

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

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

We need to plug x+hx+h into the function f(x)f(x):

f(x+h)=(x+h)2+7(x+h)+4f(x+h) = -(x+h)^2 + 7(x+h) + 4

Now expand this expression:

f(x+h)=(x2+2xh+h2)+7(x+h)+4f(x+h) = -(x^2 + 2xh + h^2) + 7(x+h) + 4 =x22xhh2+7x+7h+4= -x^2 - 2xh - h^2 + 7x + 7h + 4

Step 2: Find 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)=(x22xhh2+7x+7h+4)(x2+7x+4)f(x+h) - f(x) = (-x^2 - 2xh - h^2 + 7x + 7h + 4) - (-x^2 + 7x + 4) =x22xhh2+7x+7h+4+x27x4= -x^2 - 2xh - h^2 + 7x + 7h + 4 + x^2 - 7x - 4 Simplify: =2xhh2+7h= -2xh - h^2 + 7h

Step 3: Divide by hh

Now divide the result by hh:

f(x+h)f(x)h=2xhh2+7hh\frac{f(x+h) - f(x)}{h} = \frac{-2xh - h^2 + 7h}{h}

Simplify each term:

=2xh+7= -2x - h + 7

Final Result:

f(x+h)f(x)h=2xh+7\frac{f(x+h) - f(x)}{h} = -2x - h + 7

Would you like more details or have any further questions?

Here are 5 related questions for deeper understanding:

  1. How is the difference quotient related to the derivative of a function?
  2. What happens to the difference quotient as hh approaches 0?
  3. Why do we expand f(x+h)f(x+h) before subtracting f(x)f(x)?
  4. Can you compute the derivative of f(x)=x2+7x+4f(x) = -x^2 + 7x + 4 using the power rule and compare it with the difference quotient?
  5. How would the difference quotient change if we had a cubic function instead?

Tip: The difference quotient gives an approximation of the derivative, which represents the slope of the tangent line at any point on the curve.

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Math Problem Analysis

Mathematical Concepts

Algebra
Difference Quotient
Quadratic Functions

Formulas

Difference Quotient: (f(x+h) - f(x))/h
Quadratic Function: f(x) = ax^2 + bx + c

Theorems

Derivative Approximation via Difference Quotient

Suitable Grade Level

Grades 9-12 (High School)