Math Problem Statement

If 3x^2 + 2xy + y^2 = 2, then the value of dy/dx at x = 1 is

Solution

To solve for dydx\frac{dy}{dx} at x=1x = 1, given the equation:

3x2+2xy+y2=23x^2 + 2xy + y^2 = 2

we'll need to differentiate both sides of the equation with respect to xx using implicit differentiation.

Step 1: Differentiate each term with respect to xx

  1. For 3x23x^2, the derivative is 6x6x.
  2. For 2xy2xy, we use the product rule: ddx(2xy)=2(dxdxy+xdydx)=2y+2xdydx\frac{d}{dx}(2xy) = 2 \left(\frac{dx}{dx} \cdot y + x \cdot \frac{dy}{dx}\right) = 2y + 2x \frac{dy}{dx}
  3. For y2y^2, we use the chain rule: ddx(y2)=2ydydx\frac{d}{dx}(y^2) = 2y \frac{dy}{dx}

Step 2: Differentiate the entire equation

Differentiating each term, we get:

6x+2y+2xdydx+2ydydx=06x + 2y + 2x \frac{dy}{dx} + 2y \frac{dy}{dx} = 0

Step 3: Solve for dydx\frac{dy}{dx}

Rearrange to isolate dydx\frac{dy}{dx}:

(2x+2y)dydx=6x2y(2x + 2y) \frac{dy}{dx} = -6x - 2y

dydx=6x2y2x+2y\frac{dy}{dx} = \frac{-6x - 2y}{2x + 2y}

Step 4: Substitute x=1x = 1

To find dydx\frac{dy}{dx} at x=1x = 1, we need to determine the corresponding value of yy when x=1x = 1.

Substitute x=1x = 1 into the original equation:

3(1)2+2(1)y+y2=23(1)^2 + 2(1)y + y^2 = 2

3+2y+y2=23 + 2y + y^2 = 2

y2+2y+1=0y^2 + 2y + 1 = 0

(y+1)2=0(y + 1)^2 = 0

Thus, y=1y = -1 when x=1x = 1.

Step 5: Substitute x=1x = 1 and y=1y = -1 into dydx\frac{dy}{dx}

dydx=6(1)2(1)2(1)+2(1)\frac{dy}{dx} = \frac{-6(1) - 2(-1)}{2(1) + 2(-1)}

=6+222= \frac{-6 + 2}{2 - 2}

=40= \frac{-4}{0}

This expression is undefined due to division by zero, which suggests a vertical tangent line at x=1x = 1, y=1y = -1. Therefore, dydx\frac{dy}{dx} is undefined at this point.

Would you like a deeper explanation of any specific part, or do you have any questions?

Here are 5 additional related questions for further practice:

  1. How does implicit differentiation help in solving for dydx\frac{dy}{dx} in terms of xx and yy?
  2. What does it mean if dydx\frac{dy}{dx} is undefined at a certain point?
  3. Can you find the value of dydx\frac{dy}{dx} for other values of xx in similar problems?
  4. How would the process change if the original equation had a higher degree for xx or yy?
  5. How can you interpret a vertical tangent line in the context of graphing?

Tip: Always double-check by substituting values back into the differentiated equation to confirm whether the answer aligns with expected behavior, such as undefined slopes for vertical tangents.

Ask a new question for Free

By Image

Drop file here or Click Here to upload

Math Problem Analysis

Mathematical Concepts

Implicit Differentiation
Algebraic Manipulation

Formulas

Implicit differentiation formula for dy/dx
Product rule for derivatives: d(uv)/dx = u(dv/dx) + v(du/dx)
Chain rule for derivatives: d(y^2)/dx = 2y(dy/dx)

Theorems

Product Rule
Chain Rule

Suitable Grade Level

College Calculus