Math Problem Statement

find dy/dx given the following function xy^2 + xy^2 + 4y^2 = 0

Solution

Given the function:

xy2+xy2+4y2=0xy^2 + xy^2 + 4y^2 = 0

Let's simplify it first.

  1. Combine like terms: 2xy2+4y2=02xy^2 + 4y^2 = 0

  2. Factor out y2y^2: y2(2x+4)=0y^2(2x + 4) = 0

This equation implies two possibilities:

  1. y2=0y^2 = 0, which gives y=0y = 0.
  2. 2x+4=02x + 4 = 0, which simplifies to x=2x = -2.

Since we want to find dydx\frac{dy}{dx}, we need to proceed with implicit differentiation on the original equation to capture the derivative relationship between xx and yy.

Differentiating Implicitly

Starting from: 2xy2+4y2=02xy^2 + 4y^2 = 0

Differentiate each term with respect to xx:

  1. For 2xy22xy^2: ddx(2xy2)=2(y2+x2ydydx)=2y2+4xydydx\frac{d}{dx}(2xy^2) = 2 \left( y^2 + x \cdot 2y \frac{dy}{dx} \right) = 2y^2 + 4xy \frac{dy}{dx}

  2. For 4y24y^2: ddx(4y2)=42ydydx=8ydydx\frac{d}{dx}(4y^2) = 4 \cdot 2y \frac{dy}{dx} = 8y \frac{dy}{dx}

Thus, the differentiated equation is: 2y2+4xydydx+8ydydx=02y^2 + 4xy \frac{dy}{dx} + 8y \frac{dy}{dx} = 0

Solving for dydx\frac{dy}{dx}

Combine terms involving dydx\frac{dy}{dx}: 2y2+(4xy+8y)dydx=02y^2 + (4xy + 8y) \frac{dy}{dx} = 0

Move 2y22y^2 to the other side: (4xy+8y)dydx=2y2(4xy + 8y) \frac{dy}{dx} = -2y^2

Now, divide both sides by 4xy+8y4xy + 8y (assuming y0y \neq 0): dydx=2y24xy+8y\frac{dy}{dx} = \frac{-2y^2}{4xy + 8y}

Simplify by factoring out yy from both the numerator and denominator: dydx=2y4x+8=y2x+4\frac{dy}{dx} = \frac{-2y}{4x + 8} = \frac{-y}{2x + 4}

Final Answer

dydx=y2x+4\frac{dy}{dx} = \frac{-y}{2x + 4}

Would you like further details or have any questions about the steps?


Here are some related questions to explore:

  1. How would the solution change if the equation was xy2+3xy2+4y2=0xy^2 + 3xy^2 + 4y^2 = 0?
  2. What is the interpretation of dydx\frac{dy}{dx} if x=2x = -2?
  3. How would you find d2ydx2\frac{d^2y}{dx^2} for this function?
  4. What happens to dydx\frac{dy}{dx} if yy approaches zero?
  5. How does implicit differentiation help in finding derivatives of non-standard functions?

Tip: When differentiating implicitly, keep terms involving dydx\frac{dy}{dx} on one side to simplify solving.

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Math Problem Analysis

Mathematical Concepts

Implicit Differentiation
Algebraic Simplification
Factoring

Formulas

Implicit differentiation: d/dx(f(x, y)) = ∂f/∂x + (∂f/∂y) * (dy/dx)
Derivative of x*y^2 with respect to x: d(xy^2)/dx = y^2 + x * 2y * (dy/dx)

Theorems

Implicit Differentiation Theorem

Suitable Grade Level

Grades 11-12