Chain Rule Math Example 1

Follow the full solution, then compare it with the other examples linked below.

Example 1

easy
Find the derivative of f(x)=(3x+1)4f(x) = (3x + 1)^4.

Solution

  1. 1
    Identify the outer function u4u^4 and the inner function u=3x+1u = 3x + 1.
  2. 2
    Apply the chain rule: ddx[u4]=4u3โ‹…dudx\frac{d}{dx}[u^4] = 4u^3 \cdot \frac{du}{dx}.
  3. 3
    The derivative of the inner function: dudx=3\frac{du}{dx} = 3.
  4. 4
    Combine: fโ€ฒ(x)=4(3x+1)3โ‹…3=12(3x+1)3f'(x) = 4(3x+1)^3 \cdot 3 = 12(3x+1)^3.

Answer

fโ€ฒ(x)=12(3x+1)3f'(x) = 12(3x + 1)^3
The chain rule says: differentiate the outer function, keep the inner function, then multiply by the derivative of the inner function. Think of it as peeling layers.

About Chain Rule

The derivative of a composite function f(g(x))f(g(x)) equals fโ€ฒ(g(x))โ‹…gโ€ฒ(x)f'(g(x)) \cdot g'(x): the derivative of the outer function evaluated at the inner, times the derivative of the inner.

Learn more about Chain Rule โ†’

More Chain Rule Examples