Math Problem Statement

what is dy/dx for 2x^3-5xy-y^2=3

Solution

We are asked to find dydx\frac{dy}{dx} for the equation:

2x35xyy2=32x^3 - 5xy - y^2 = 3

Since this equation involves both xx and yy, we need to use implicit differentiation. Let's proceed step by step.

Step 1: Differentiate each term with respect to xx

  1. ddx(2x3)=6x2\frac{d}{dx}(2x^3) = 6x^2
  2. ddx(5xy)\frac{d}{dx}(-5xy) — This requires the product rule: ddx(5xy)=5(ddx(xy))=5(1y+xdydx)=5y5xdydx\frac{d}{dx}(-5xy) = -5\left(\frac{d}{dx}(x \cdot y)\right) = -5\left(1 \cdot y + x \cdot \frac{dy}{dx}\right) = -5y - 5x \frac{dy}{dx}
  3. ddx(y2)=2ydydx\frac{d}{dx}(-y^2) = -2y \frac{dy}{dx} — Since yy is a function of xx, we apply the chain rule.

Step 2: Differentiate the right-hand side

ddx(3)=0\frac{d}{dx}(3) = 0

Step 3: Combine the results

After differentiating each term, we get:

6x25y5xdydx2ydydx=06x^2 - 5y - 5x \frac{dy}{dx} - 2y \frac{dy}{dx} = 0

Step 4: Solve for dydx\frac{dy}{dx}

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

6x25y=5xdydx+2ydydx6x^2 - 5y = 5x \frac{dy}{dx} + 2y \frac{dy}{dx}

Factor out dydx\frac{dy}{dx} on the right-hand side:

6x25y=(5x+2y)dydx6x^2 - 5y = \left(5x + 2y\right) \frac{dy}{dx}

Finally, divide both sides by 5x+2y5x + 2y to isolate dydx\frac{dy}{dx}:

dydx=6x25y5x+2y\frac{dy}{dx} = \frac{6x^2 - 5y}{5x + 2y}

This is the derivative dydx\frac{dy}{dx}.


Would you like more details on any part of this process or have any further questions?

Here are 5 related questions to expand on this topic:

  1. What is the product rule, and how does it apply in implicit differentiation?
  2. Can you show how to solve another implicit differentiation problem with a trigonometric function?
  3. How do you apply the chain rule when differentiating composite functions?
  4. Why do we need implicit differentiation when differentiating functions involving both xx and yy?
  5. How would the solution change if the original equation was 2x35xy+y2=32x^3 - 5xy + y^2 = 3?

Tip: When differentiating terms like xyxy, always apply the product rule, since both xx and yy are functions of xx.

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Math Problem Analysis

Mathematical Concepts

Implicit Differentiation
Product Rule
Chain Rule

Formulas

Implicit differentiation: d/dx(f(x, y)) = 0
Product rule: d/dx(uv) = u'v + uv'
Chain rule: d/dx(f(y)) = f'(y) dy/dx

Theorems

Implicit Differentiation Theorem

Suitable Grade Level

Grades 11-12 or early college