Math Problem Statement

solve

If 2x^2 - 3y^2 = 2, find the two values of dy/dx when x = 5.

Solution

We are given the equation:

2x23y2=22x^2 - 3y^2 = 2

Step 1: Differentiate both sides implicitly

Differentiate both terms with respect to xx:

ddx(2x2)ddx(3y2)=ddx(2)\frac{d}{dx} (2x^2) - \frac{d}{dx} (3y^2) = \frac{d}{dx} (2)

Using the power rule:

4x6ydydx=04x - 6y \frac{dy}{dx} = 0

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

Rearrange the equation:

6ydydx=4x-6y \frac{dy}{dx} = -4x

dydx=4x6y=2x3y\frac{dy}{dx} = \frac{4x}{6y} = \frac{2x}{3y}

Step 3: Find values at x=5x = 5

We substitute x=5x = 5 into the original equation to find yy:

2(52)3y2=22(5^2) - 3y^2 = 2

503y2=250 - 3y^2 = 2

3y2=483y^2 = 48

y2=16y^2 = 16

y=±4y = \pm 4

Step 4: Compute dydx\frac{dy}{dx} for both values of yy

For y=4y = 4:

dydx=2(5)3(4)=1012=56\frac{dy}{dx} = \frac{2(5)}{3(4)} = \frac{10}{12} = \frac{5}{6}

For y=4y = -4:

dydx=2(5)3(4)=1012=56\frac{dy}{dx} = \frac{2(5)}{3(-4)} = \frac{10}{-12} = -\frac{5}{6}

Final Answer:

The two values of dydx\frac{dy}{dx} when x=5x = 5 are:

56,56\frac{5}{6}, \quad -\frac{5}{6}

Would you like a detailed explanation of any step?

Here are five related questions to explore further:

  1. How do you apply implicit differentiation to more complex equations?
  2. What is the geometric interpretation of having two values for dydx\frac{dy}{dx}?
  3. How does implicit differentiation differ from explicit differentiation?
  4. Can you use a different method to find dydx\frac{dy}{dx} for this problem?
  5. What happens if we solve for yy explicitly before differentiating?

Tip: Always check for both positive and negative values of yy when solving for derivatives implicitly!

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Math Problem Analysis

Mathematical Concepts

Implicit Differentiation
Derivatives
Algebraic Manipulation

Formulas

Implicit Differentiation: d/dx [f(x, y) = 0]
Power Rule: d/dx [x^n] = n*x^(n-1)

Theorems

Implicit Differentiation Theorem

Suitable Grade Level

Grades 11-12