How Do You Apply the Chain Rule to Differentiate f(x) = x^5(4^(x^2))?

In summary, To find the derivative of the given function f(x) = x^5(4^(x^2)), the product rule should be used first and then differentiate 4^(x^2) using the formula d/dx ( a^(f(x)) ) = a^f(x) * ln(a) * f'(x) derived from the chain rule. The derivative of 4^(x^2) is 2x 4^(x^2) ln 4. The key is to remember that the derivative of ax is ax ln a.
  • #1
ninanana
3
0
I'm so confused. I have to find the derivative of f(x) = x^5(4^(x^2)). All of the powers are messing me up. Any help would be much appreciated. Thanks!
 
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  • #2
Is your function [tex]f(x) = x^5(4^{x^2})[/tex] or [tex]f(x) = x^{5(4^{x^2})}[/tex] ?
 
Last edited:
  • #3
The first one, sorry.
 
  • #4
Use product rule first, then you end up differentiating 4^(x^2).
A nice formula to know is d/dx ( a^(f(x)) ) = a^f(x) * ln(a) * f'(x), which comes from the chain rule.
 
  • #5
I know I'm having some sort of stupid lapse right now, but the part I can't figure out is the 4^(x^2).
 
  • #6
To differentiate [tex]y= 4^{x^2}[/tex], take the logarithm of both sides:
[tex]ln y= x^2 ln 4[/tex]
Now differentiate that, with respect to x.
[tex]\frac{1}{y}y'= 2x ln 4[/tex]
so
[tex]y'= 2x (ln 4)y= 2x 4^{x^2} ln 4[/tex]

Karlsen used the fact that the derivative of ax is ax ln a, but not everyone knows that!
 

1. What is the chain rule in calculus?

The chain rule is a rule in calculus that allows us to find the derivative of a composite function, which is a function that is made up of two or more functions. It states that the derivative of a composite function is equal to the derivative of the outer function multiplied by the derivative of the inner function.

2. How do you apply the chain rule?

To apply the chain rule, you first need to identify the outer function and the inner function. Then, take the derivative of the outer function, leaving the inner function unchanged. Next, take the derivative of the inner function and multiply it by the derivative of the outer function. Finally, substitute the inner function back into the equation to get the final derivative.

3. Why is the chain rule important?

The chain rule is important because it allows us to find the derivative of more complex functions by breaking them down into simpler functions. It is a fundamental rule in calculus and is used in various applications, such as optimization, physics, and engineering.

4. Can you provide an example of the chain rule?

Sure, let's say we have the function f(x) = (x^3 + 2x)^4. To find the derivative of this function, we can use the chain rule. First, we identify the outer function as (x^4) and the inner function as (x^3 + 2x). Then, taking the derivative of the outer function, we get 4x^3. Next, taking the derivative of the inner function, we get 3x^2 + 2. Finally, we substitute the inner function back into the equation to get the final derivative: 4(x^3 + 2x)^3(3x^2 + 2).

5. How can I remember the chain rule?

One way to remember the chain rule is by using the acronym "UDU" which stands for "undo, differentiate, undo." This reminds us to first undo the outer function, then differentiate it, and finally undo the inner function. Another way is to practice using the rule in various examples until it becomes second nature.

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