Math Problem Statement

Evaluate dy/dx for y = sqrt((x + 1)(1 + 2x))

Solution

To find dydx\frac{dy}{dx} for the function y=(x+1)(1+2x)y = \sqrt{(x+1)(1+2x)}, we will use the chain rule and the product rule for differentiation.

Let's go through the steps:

  1. Rewrite the function for easier differentiation: y=(x+1)(1+2x)=((x+1)(1+2x))12y = \sqrt{(x+1)(1+2x)} = ((x+1)(1+2x))^{\frac{1}{2}}

  2. Differentiate using the chain rule: Let u=(x+1)(1+2x)u = (x+1)(1+2x), so y=u12y = u^{\frac{1}{2}}.

    Then, dydx=12u12dudx=12ududx\frac{dy}{dx} = \frac{1}{2} u^{-\frac{1}{2}} \cdot \frac{du}{dx} = \frac{1}{2\sqrt{u}} \cdot \frac{du}{dx}

  3. Differentiate u=(x+1)(1+2x)u = (x+1)(1+2x) using the product rule: dudx=(x+1)ddx(1+2x)+(1+2x)ddx(x+1)\frac{du}{dx} = (x+1) \cdot \frac{d}{dx}(1+2x) + (1+2x) \cdot \frac{d}{dx}(x+1)

    Calculating each derivative:

    • ddx(1+2x)=2\frac{d}{dx}(1+2x) = 2
    • ddx(x+1)=1\frac{d}{dx}(x+1) = 1

    So, dudx=(x+1)2+(1+2x)1=2(x+1)+(1+2x)\frac{du}{dx} = (x+1) \cdot 2 + (1+2x) \cdot 1 = 2(x+1) + (1+2x) Simplify this: dudx=2x+2+1+2x=4x+3\frac{du}{dx} = 2x + 2 + 1 + 2x = 4x + 3

  4. Substitute back into the expression for dydx\frac{dy}{dx}: Since u=(x+1)(1+2x)u = (x+1)(1+2x), dydx=12(x+1)(1+2x)(4x+3)\frac{dy}{dx} = \frac{1}{2\sqrt{(x+1)(1+2x)}} \cdot (4x + 3)

Thus, the derivative is: dydx=4x+32(x+1)(1+2x)\frac{dy}{dx} = \frac{4x + 3}{2\sqrt{(x+1)(1+2x)}}

Would you like further details or have any questions?

Here are some additional questions for deeper understanding:

  1. How would you approach finding d2ydx2\frac{d^2y}{dx^2} for this function?
  2. What is the behavior of dydx\frac{dy}{dx} as xx \to \infty?
  3. How does the chain rule apply when there’s a nested square root in the function?
  4. Can you identify any points where dydx\frac{dy}{dx} might be undefined?
  5. How would you verify the correctness of this derivative using a different method?

Tip: Always simplify expressions inside the square root when possible, as it may reveal additional symmetries or allow for easier further differentiation.

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Math Problem Analysis

Mathematical Concepts

Differentiation
Chain Rule
Product Rule
Algebraic Simplification

Formulas

Chain rule: d/dx [f(g(x))] = f'(g(x)) * g'(x)
Product rule: d/dx [u*v] = u'v + uv'

Theorems

Chain Rule
Product Rule

Suitable Grade Level

Grades 11-12