Math Problem Statement

If f(x) = 1/(x+1), evaluate the difference quotient (f(x+h) - f(x))/h.

Solution

The problem asks us to evaluate the difference quotient for the given function f(x)=1x+1f(x) = \frac{1}{x+1}. The difference quotient is the expression:

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

Step-by-step solution:

  1. Substitute f(x)=1x+1f(x) = \frac{1}{x+1} and f(x+h)f(x+h) into the difference quotient formula:

    f(x+h)=1(x+h)+1=1x+h+1f(x+h) = \frac{1}{(x+h)+1} = \frac{1}{x+h+1}

    So the difference quotient becomes:

    f(x+h)f(x)h=1x+h+11x+1h\frac{f(x+h) - f(x)}{h} = \frac{\frac{1}{x+h+1} - \frac{1}{x+1}}{h}

  2. Combine the fractions in the numerator:

    We need a common denominator to subtract these two fractions. The common denominator will be (x+h+1)(x+1)(x+h+1)(x+1). So:

    1x+h+11x+1=(x+1)(x+h+1)(x+h+1)(x+1)\frac{1}{x+h+1} - \frac{1}{x+1} = \frac{(x+1) - (x+h+1)}{(x+h+1)(x+1)}

  3. Simplify the numerator:

    The numerator simplifies as follows:

    (x+1)(x+h+1)=x+1xh1=h(x+1) - (x+h+1) = x+1 - x - h - 1 = -h

    So we now have:

    h(x+h+1)(x+1)\frac{-h}{(x+h+1)(x+1)}

  4. Substitute back into the difference quotient:

    Now, the expression for the difference quotient becomes:

    h(x+h+1)(x+1)h\frac{\frac{-h}{(x+h+1)(x+1)}}{h}

  5. Simplify the expression:

    Dividing by hh is the same as multiplying by 1h\frac{1}{h}, so:

    hh(x+h+1)(x+1)=1(x+h+1)(x+1)\frac{-h}{h(x+h+1)(x+1)} = \frac{-1}{(x+h+1)(x+1)}

Final result:

f(x+h)f(x)h=1(x+h+1)(x+1)\frac{f(x+h) - f(x)}{h} = \frac{-1}{(x+h+1)(x+1)}

This is the simplified form of the difference quotient for the function f(x)=1x+1f(x) = \frac{1}{x+1}.

Would you like further details on any step or have any other questions?

Here are 5 related questions:

  1. How does this difference quotient relate to the derivative of the function?
  2. Can we simplify the difference quotient further when h0h \to 0?
  3. What is the geometric interpretation of the difference quotient?
  4. How do you compute the derivative of a rational function like f(x)=1x+1f(x) = \frac{1}{x+1}?
  5. How does this method apply to other functions of similar forms?

Tip: The difference quotient is a fundamental concept in calculus as it forms the basis for the definition of the derivative.

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Math Problem Analysis

Mathematical Concepts

Calculus
Difference Quotient
Rational Functions

Formulas

Difference quotient formula: (f(x+h) - f(x)) / h
f(x) = 1/(x+1)

Theorems

Limit Definition of Derivative

Suitable Grade Level

Grades 11-12, College Level