Math Problem Statement

Write the composite function in the form f(g(x)). Identify the inner function u = g(x) and the outer function y = f(u) for y = e^(9√x). Find the derivative dy/dx.

Solution

To solve this problem, let's break down the composite function y=e9xy = e^{9\sqrt{x}} into inner and outer functions as y=f(g(x))y = f(g(x)).

Step 1: Identify f(u)f(u) and g(x)g(x)

We want to express y=e9xy = e^{9\sqrt{x}} in terms of two functions:

  1. Inner function g(x)g(x): Let g(x)=9xg(x) = 9\sqrt{x}.
  2. Outer function f(u)f(u): Then, f(u)=euf(u) = e^u.

So, we can write: f(u)=euandg(x)=9x.f(u) = e^u \quad \text{and} \quad g(x) = 9\sqrt{x}.

This makes y=f(g(x))y = f(g(x)).

Step 2: Find the derivative dydx\frac{dy}{dx}

To find dydx\frac{dy}{dx}, we’ll use the chain rule: dydx=f(g(x))g(x).\frac{dy}{dx} = f'(g(x)) \cdot g'(x).

Step 2a: Find f(u)f'(u)

Since f(u)=euf(u) = e^u, the derivative f(u)=euf'(u) = e^u.

Step 2b: Find g(x)g'(x)

Since g(x)=9x=9x1/2g(x) = 9\sqrt{x} = 9x^{1/2}, we differentiate with respect to xx: g(x)=912x12=92x.g'(x) = 9 \cdot \frac{1}{2} x^{-\frac{1}{2}} = \frac{9}{2\sqrt{x}}.

Step 2c: Substitute and simplify

Now, substitute f(g(x))=e9xf'(g(x)) = e^{9\sqrt{x}} and g(x)=92xg'(x) = \frac{9}{2\sqrt{x}}: dydx=e9x92x=9e9x2x.\frac{dy}{dx} = e^{9\sqrt{x}} \cdot \frac{9}{2\sqrt{x}} = \frac{9e^{9\sqrt{x}}}{2\sqrt{x}}.

Final Answer:

  1. f(u)=euf(u) = e^u and g(x)=9xg(x) = 9\sqrt{x}.
  2. dydx=9e9x2x\frac{dy}{dx} = \frac{9e^{9\sqrt{x}}}{2\sqrt{x}}.

Would you like further details on any of these steps, or do you have questions?


Here are 5 related questions to expand on this topic:

  1. How would you apply the chain rule to a different composite function, such as y=sin(3x2)y = \sin(3x^2)?
  2. What if the exponent in the outer function were different, like y=e5xy = e^{5\sqrt{x}}? How would that affect the derivative?
  3. Can you identify f(u)f(u) and g(x)g(x) in a similar function, y=ln(x2+1)y = \ln(x^2 + 1)?
  4. How does the chain rule differ from the product rule in differentiation?
  5. How would the derivative change if g(x)=9x3/2g(x) = 9x^{3/2} instead?

Tip: Always identify inner and outer functions clearly in composite functions; this simplifies applying the chain rule effectively.

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Math Problem Analysis

Mathematical Concepts

Composite functions
Chain rule
Exponential functions
Differentiation

Formulas

Composite function: y = f(g(x))
Chain rule: dy/dx = f'(g(x)) * g'(x)
Derivative of exponential function: d/dx(e^u) = e^u * du/dx

Theorems

Chain rule

Suitable Grade Level

Grades 11-12