Calc Midterm, First Year University (derivative related stuff)

In summary, the constant "a" can be found by using the chain rule to differentiate f(x)=x^x and setting it equal to 2x^x.
  • #1
y2klimen
1
0

Homework Statement


If f(x)=x^x for x>0, find the constant a such that f'(a)=2f(a)


Homework Equations





The Attempt at a Solution


f'(a)=a*a^(a-1)
=a^a

2f(a)=2a^a

2a^a=a^a
ln2a^a=lna^a
aln2a=alna

...?
 
Physics news on Phys.org
  • #2
If f(x) = x^x, then f'(x) =/= x*x^(x-1). That rule works if your exponent is a number, not a function. Rewrite x^x in exponential form and then differentiate using the chain rule to find f'(x).
 
  • #3
y2klimen said:

Homework Statement


If f(x)=x^x for x>0, find the constant a such that f'(a)=2f(a)


Homework Equations





The Attempt at a Solution


f'(a)=a*a^(a-1)
=a^a

2f(a)=2a^a

2a^a=a^a
ln2a^a=lna^a
aln2a=alna

...?
No that is not right. You cannot treat a (x) as a variable in one case (the base) and a constant in the other (the exponent).

If y= xx then ln(y)= x ln(x). Use the chain rule to find dy/dx.
 

1. What is a derivative?

A derivative is a mathematical concept that represents the rate of change of a function at a specific point. It is denoted by f'(x) or dy/dx.

2. What is the purpose of finding derivatives?

Derivatives are used to solve various problems in calculus, such as finding the maximum or minimum value of a function, determining the slope of a curve, and analyzing the behavior of a function at a specific point.

3. How do I find the derivative of a function?

To find the derivative of a function, you can use the power rule, product rule, quotient rule, or chain rule. These rules involve different formulas and techniques for finding the derivative of a specific type of function.

4. What is the difference between the first and second derivative?

The first derivative represents the rate of change of a function, while the second derivative represents the rate of change of the first derivative. In other words, the second derivative measures the rate of change of the slope of a function.

5. How can I use derivatives to solve real-world problems?

Derivatives are used in many fields, such as physics, economics, and engineering, to model and analyze real-world phenomena. For example, derivatives can be used to determine the optimal production level for a company or to calculate the velocity of an object in motion.

Similar threads

  • Calculus and Beyond Homework Help
Replies
2
Views
907
  • Calculus and Beyond Homework Help
Replies
2
Views
1K
  • Calculus and Beyond Homework Help
Replies
7
Views
299
  • Calculus and Beyond Homework Help
Replies
6
Views
896
  • Calculus and Beyond Homework Help
Replies
1
Views
1K
  • Calculus and Beyond Homework Help
Replies
22
Views
2K
  • Calculus and Beyond Homework Help
Replies
8
Views
479
  • Calculus and Beyond Homework Help
Replies
4
Views
2K
  • Calculus and Beyond Homework Help
Replies
2
Views
973
  • Calculus and Beyond Homework Help
Replies
1
Views
771
Back
Top