Finding Derivatives with the Multivariable Chain Rule

In summary, the conversation discusses using the multi-variable chain rule to show that the expression 2∂z/∂x − ∂z/∂y equals 0 for a differentiable function of one variable. The conversation also mentions using the chain rule for ∂z/∂x and ∂z/∂y.
  • #1
Doug_West
9
0

Homework Statement



Let f be a differentiable function of one variable, and let
z = f(x + 2y). Show that
2∂z/∂x − ∂z/∂y = 0

Homework Equations



Multi-variable chain rule

The Attempt at a Solution



I have no idea where to start with this, any advice would be greatly appreciated.

Thanks in advance,
Doug
 
Physics news on Phys.org
  • #2
Doug_West said:

Homework Statement



Let f be a differentiable function of one variable, and let
z = f(x + 2y). Show that
2∂z/∂x − ∂z/∂y = 0

Homework Equations



Multi-variable chain rule

The Attempt at a Solution



I have no idea where to start with this, any advice would be greatly appreciated.

Thanks in advance,
Doug

z=f(g(x,y)), where g(x,y)=x+2y. Now what does the chain rule tell you about, say ∂z/∂x?
 
  • #3
would it be f'(g(x,y))*1?
 
  • #4
Doug_West said:
would it be f'(g(x,y))*1?

Yes! Now do ∂z/∂y.
 
  • #5
f'(g(x,y)))*2
 
  • #6
So 2∂z/∂x − ∂z/∂y equals what?
 
  • #7
0! Thanks for the help.

Doug.
 

1. What is the Multivariable Chain Rule?

The Multivariable Chain Rule is a mathematical concept that is used to find the derivatives of functions with multiple variables. It states that the derivative of a composition of two or more functions is equal to the product of the derivatives of those functions.

2. When is the Multivariable Chain Rule used?

The Multivariable Chain Rule is used when a function has multiple independent variables and is composed of multiple functions. It is commonly used in multivariable calculus and in physics and engineering applications.

3. How is the Multivariable Chain Rule applied?

To apply the Multivariable Chain Rule, you must first identify the composite function and then take the derivative of each individual function. Finally, you multiply the derivatives together to find the overall derivative.

4. What is the difference between the Multivariable Chain Rule and the Single Variable Chain Rule?

The Multivariable Chain Rule is used to find the derivatives of functions with multiple variables, while the Single Variable Chain Rule is used for functions with only one variable. The Multivariable Chain Rule involves taking partial derivatives, while the Single Variable Chain Rule involves taking ordinary derivatives.

5. Are there any special cases or exceptions to the Multivariable Chain Rule?

Yes, there are some special cases where the Multivariable Chain Rule may not apply, such as when the function is not differentiable or when there are discontinuities in the function. It is important to check the assumptions and conditions of the rule before applying it to a particular function.

Similar threads

  • Calculus and Beyond Homework Help
Replies
2
Views
916
  • Calculus and Beyond Homework Help
Replies
3
Views
904
  • Calculus and Beyond Homework Help
Replies
4
Views
971
  • Calculus and Beyond Homework Help
Replies
1
Views
704
  • Calculus and Beyond Homework Help
Replies
9
Views
2K
  • Calculus and Beyond Homework Help
Replies
3
Views
1K
  • Calculus and Beyond Homework Help
Replies
4
Views
996
  • Calculus and Beyond Homework Help
Replies
3
Views
1K
  • Calculus and Beyond Homework Help
Replies
2
Views
966
  • Calculus and Beyond Homework Help
Replies
10
Views
1K
Back
Top