Math Problem Statement

Find the derivative of y = (8 - 3x^3)^3 at x = 2.

Solution

To find the derivative of y=(83x3)3y = (8 - 3x^3)^3 at x=2x = 2, we first find the derivative of yy with respect to xx using the chain rule:

  1. Differentiate the outer function: If u=83x3u = 8 - 3x^3, then y=u3y = u^3. The derivative of yy with respect to uu is dydu=3u2\frac{dy}{du} = 3u^2.

  2. Differentiate the inner function: The derivative of u=83x3u = 8 - 3x^3 with respect to xx is dudx=9x2\frac{du}{dx} = -9x^2.

  3. Apply the chain rule: Combine these derivatives: dydx=dydududx=3u2(9x2)=27u2x2\frac{dy}{dx} = \frac{dy}{du} \cdot \frac{du}{dx} = 3u^2 \cdot (-9x^2) = -27u^2x^2.

Now, substitute x=2x = 2 into uu: u=83(2)3=838=824=16u = 8 - 3(2)^3 = 8 - 3 \cdot 8 = 8 - 24 = -16

Thus, dydx\frac{dy}{dx} at x=2x = 2 is: dydx=27(16)2(2)2=272564=27648\frac{dy}{dx} = -27(-16)^2 \cdot (2)^2 = -27 \cdot 256 \cdot 4 = -27648

Therefore, the derivative of yy at x=2x = 2 is 27648-27648.

Do you need a detailed breakdown or have any other questions related to this? Here are some additional questions you might consider:

  1. How would you find the second derivative of the function?
  2. How does changing the exponent from 3 to another value affect the derivative?
  3. What happens to the derivative as xx approaches infinity?
  4. How can you confirm this result using a numerical approximation?
  5. Would the derivative at x=0x = 0 be different, and how would you calculate it?

Tip: When applying the chain rule, always keep track of your inner and outer functions to correctly apply their derivatives.

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Math Problem Analysis

Mathematical Concepts

Calculus
Derivatives
Chain Rule

Formulas

Chain Rule: dy/dx = dy/du * du/dx

Theorems

Chain Rule

Suitable Grade Level

Grades 11-12