Math Problem Statement

y'' of x^3-y^3=3

Solution

To solve for yy'' (the second derivative of yy with respect to xx) of the equation x3y3=3x^3 - y^3 = 3, we will need to implicitly differentiate both sides of the equation.

Given:

x3y3=3x^3 - y^3 = 3

Step 1: Differentiate implicitly with respect to xx.

Differentiating both sides of the equation with respect to xx, we treat yy as a function of xx (i.e., y=y(x)y = y(x)):

ddx(x3)ddx(y3)=ddx(3)\frac{d}{dx}(x^3) - \frac{d}{dx}(y^3) = \frac{d}{dx}(3)

This gives:

3x23y2dydx=03x^2 - 3y^2 \frac{dy}{dx} = 0

Step 2: Solve for dydx\frac{dy}{dx}.

Now, solve for dydx\frac{dy}{dx}:

3x2=3y2dydx3x^2 = 3y^2 \frac{dy}{dx}

Divide both sides by 3y23y^2:

dydx=x2y2\frac{dy}{dx} = \frac{x^2}{y^2}

Step 3: Differentiate again to find yy''.

Now, differentiate dydx=x2y2\frac{dy}{dx} = \frac{x^2}{y^2} implicitly to get the second derivative yy'':

ddx(dydx)=ddx(x2y2)\frac{d}{dx} \left( \frac{dy}{dx} \right) = \frac{d}{dx} \left( \frac{x^2}{y^2} \right)

Using the quotient rule on the right-hand side:

ddx(x2y2)=2xy2x22ydydxy4\frac{d}{dx} \left( \frac{x^2}{y^2} \right) = \frac{2x y^2 - x^2 \cdot 2y \frac{dy}{dx}}{y^4}

Now substitute dydx=x2y2\frac{dy}{dx} = \frac{x^2}{y^2} into this:

y=2xy2x22yx2y2y4y'' = \frac{2x y^2 - x^2 \cdot 2y \cdot \frac{x^2}{y^2}}{y^4}

Simplify the expression:

y=2xy22x4y/y2y4y'' = \frac{2x y^2 - 2x^4 y / y^2}{y^4}

y=2xy22x4/yy4y'' = \frac{2x y^2 - 2x^4 / y}{y^4}

This is the second derivative yy''.


Do you need further details or clarification on any of the steps? Here are some related questions you might find interesting:

  1. How can we apply implicit differentiation in other types of equations?
  2. What is the quotient rule and how is it used in differentiation?
  3. Can this method be applied to higher-order derivatives?
  4. How do you solve for yy' and yy'' in parametric equations?
  5. What other methods exist for solving implicit differentiation problems?

Tip: Always simplify the expression at each step to avoid unnecessary complexity.

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Math Problem Analysis

Mathematical Concepts

Implicit Differentiation
Second Derivative
Quotient Rule

Formulas

Implicit Differentiation: d/dx(x^3 - y^3) = 0
Quotient Rule: d/dx(f(x)/g(x)) = (g(x)f'(x) - f(x)g'(x)) / g(x)^2

Theorems

Implicit Differentiation
Quotient Rule

Suitable Grade Level

Grades 11-12