Math Problem Statement

Derivation

Find the derivative of f(x) = x / sqrt(x + 1).

Solution

To find the derivative of the function f(x)=xx+1f(x) = \frac{x}{\sqrt{x+1}}, we can use the Quotient Rule, which states that if f(x)=u(x)v(x)f(x) = \frac{u(x)}{v(x)}, then f(x)=uvuvv2f'(x) = \frac{u'v - uv'}{v^2}.

In this case, we define:

  • u(x)=xu(x) = x
  • v(x)=x+1v(x) = \sqrt{x+1}

Step 1: Find uu' and vv'

  1. u(x)=xu(x) = x so u=1u' = 1.
  2. v(x)=x+1=(x+1)1/2v(x) = \sqrt{x+1} = (x+1)^{1/2}. To differentiate, we use the chain rule: v=12(x+1)1/21=12x+1.v' = \frac{1}{2}(x+1)^{-1/2} \cdot 1 = \frac{1}{2\sqrt{x+1}}.

Step 2: Apply the Quotient Rule

Now, substitute uu, uu', vv, and vv' into the Quotient Rule formula: f(x)=uvuvv2.f'(x) = \frac{u'v - uv'}{v^2}.

Substitute the values: f(x)=(1)x+1x12x+1(x+1)2.f'(x) = \frac{(1) \cdot \sqrt{x+1} - x \cdot \frac{1}{2\sqrt{x+1}}}{(\sqrt{x+1})^2}.

Step 3: Simplify the Expression

  1. The denominator simplifies as follows: (x+1)2=x+1.(\sqrt{x+1})^2 = x + 1.

  2. For the numerator: x+1x2x+1=2(x+1)x2x+1=x+22x+1.\sqrt{x+1} - \frac{x}{2\sqrt{x+1}} = \frac{2(x+1) - x}{2\sqrt{x+1}} = \frac{x+2}{2\sqrt{x+1}}.

So the derivative is: f(x)=x+22(x+1)3/2.f'(x) = \frac{x+2}{2(x+1)^{3/2}}.

Would you like further details or clarification on any steps?

Related Questions

  1. How can we verify this derivative using a different method?
  2. What is the second derivative of f(x)f(x)?
  3. How does this function behave as xx approaches infinity?
  4. Can we find the critical points of f(x)f(x)?
  5. What is the behavior of f(x)f(x) as xx approaches -1?

Tip

When using the Quotient Rule, it helps to simplify each derivative term separately before combining them.

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Math Problem Analysis

Mathematical Concepts

Calculus
Differentiation
Quotient Rule
Chain Rule

Formulas

Quotient Rule: f'(x) = (u'v - uv') / v^2
Chain Rule

Theorems

Quotient Rule
Chain Rule

Suitable Grade Level

Grades 11-12