Implicit partial derivative

  • Thread starter Calpalned
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  • #1
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6

Homework Statement


Find (∂z/∂x) of 6xyz

Homework Equations


N/a

The Attempt at a Solution


The correct answer is 6xy(∂z/∂x) but I would like proof of it. I got something different when I tried taking the partial derivative.

6xyz = 6x(yz) = Multiplication rule for derivatives

6(∂x/∂x) + y(∂z/∂x)

What did I do wrong? Thanks
 

Answers and Replies

  • #2
34,667
6,379

Homework Statement


Find (∂z/∂x) of 6xyz
Is this the complete problem statement? Generally speaking you don't find "∂z/∂x" of something, and more than you find "dy/dx" of something. You can, however, find the derivative with respect to, say, x of a function (denoted d/dx(f)) or the partial of some function with respect to, say z (denoted ∂/∂x(f).

The symbols ∂z/∂x and dy/dx represent derivatives, whereas the symbols ∂/∂x and d/dx represent operators that can be applied to functions.

Please verify that what you're providing is the complete problem statement.
Calpalned said:

Homework Equations


N/a

The Attempt at a Solution


The correct answer is 6xy(∂z/∂x) but I would like proof of it. I got something different when I tried taking the partial derivative.

6xyz = 6x(yz) = Multiplication rule for derivatives

6(∂x/∂x) + y(∂z/∂x)

What did I do wrong? Thanks
 
  • #3
297
6
The full question is find (∂z/∂x) of x3 + y3 + z3 + 6xyz = 1
My textbook says the partial derivative is 3x2 + 3z2(∂z/∂x) + 6xy(∂z/∂x) = 0
I don't get how to take the derivative of the red part.
 
  • #4
297
6
The full question is find (∂z/∂x) of x3 + y3 + z3 + 6xyz = 1
My textbook says the partial derivative is 3x2 + 3z2(∂z/∂x) + 6xy(∂z/∂x) = 0
I don't get how to take the derivative of the red part.
The derivative above is from my textbook's solutions guide.
 
  • #5
34,667
6,379
The full question is find (∂z/∂x) of x3 + y3 + z3 + 6xyz = 1
My textbook says the partial derivative is 3x2 + 3z2(∂z/∂x) + 6xy(∂z/∂x) = 0
I don't get how to take the derivative of the red part.
Corrected to: find (∂z/∂x) of if x3 + y3 + z3 + 6xyz = 1

It looks to me like there's a mistake in the solution guide.
##∂/∂x(x^3) = 3x^2## and ##∂/∂x(y^3) = 0## and ##∂/∂x(z^3) = 3z^2 ∂z/∂x##

BUT
##∂/∂x(6xyz) = 6yz## if z is independent of x, in which case ∂z/∂x would be 0. However, if z is dependent on x, you need to use the product rule. Since you're asked to find ∂z/∂x, it must be the case that z is a function of x (is dependent on x).
 

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