Math Problem Statement

If y = e^{x^3}, then d^2y/dx^2 = ?

Solution

To solve this problem, we are asked to find the second derivative of y=ex3y = e^{x^3}, which is d2ydx2\frac{d^2y}{dx^2}.

Step 1: First derivative dydx\frac{dy}{dx}

We start by finding the first derivative of y=ex3y = e^{x^3}. Using the chain rule:

dydx=ddx(ex3)=ex3ddx(x3)=ex33x2\frac{dy}{dx} = \frac{d}{dx} \left( e^{x^3} \right) = e^{x^3} \cdot \frac{d}{dx} (x^3) = e^{x^3} \cdot 3x^2

So, the first derivative is:

dydx=3x2ex3\frac{dy}{dx} = 3x^2 e^{x^3}

Step 2: Second derivative d2ydx2\frac{d^2y}{dx^2}

Now, we need to differentiate dydx=3x2ex3\frac{dy}{dx} = 3x^2 e^{x^3} again, using the product rule. The product rule states that:

ddx(f(x)g(x))=f(x)g(x)+f(x)g(x)\frac{d}{dx} \left( f(x) g(x) \right) = f'(x) g(x) + f(x) g'(x)

Let f(x)=3x2f(x) = 3x^2 and g(x)=ex3g(x) = e^{x^3}.

  • f(x)=ddx(3x2)=6xf'(x) = \frac{d}{dx} (3x^2) = 6x
  • g(x)=ddx(ex3)=ex33x2g'(x) = \frac{d}{dx} \left( e^{x^3} \right) = e^{x^3} \cdot 3x^2

Now applying the product rule:

d2ydx2=6xex3+3x2(3x2ex3)\frac{d^2y}{dx^2} = 6x e^{x^3} + 3x^2 \cdot (3x^2 e^{x^3})

Simplifying the second term:

3x23x2=9x43x^2 \cdot 3x^2 = 9x^4

Thus, the second derivative becomes:

d2ydx2=6xex3+9x4ex3\frac{d^2y}{dx^2} = 6x e^{x^3} + 9x^4 e^{x^3}

We can factor out ex3e^{x^3}:

d2ydx2=(6x+9x4)ex3\frac{d^2y}{dx^2} = \left( 6x + 9x^4 \right) e^{x^3}

Final Answer:

The correct option is:

(6x+9x4)ex3\boxed{(6x + 9x^4)e^{x^3}}

This corresponds to the first option in the list.

Would you like further details on this? Here are 5 related questions to deepen your understanding:

  1. How do you apply the chain rule to exponential functions?
  2. What is the product rule and when do you use it?
  3. How can you extend this to higher-order derivatives?
  4. What is the general approach for differentiating composite functions like exne^{x^n}?
  5. How do you factor out common terms after differentiation?

Tip: When applying the product and chain rules, breaking down each term separately can help avoid errors in longer derivatives.

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Math Problem Analysis

Mathematical Concepts

Calculus
Differentiation
Chain Rule
Product Rule

Formulas

First derivative: dy/dx = 3x^2 e^{x^3}
Second derivative: d^2y/dx^2 = (6x + 9x^4) e^{x^3}

Theorems

Chain Rule
Product Rule

Suitable Grade Level

Grade 12 / College level