Partial derivative problem

[hajfajv]

Hello
I have this problem and I cannot figure out what I'm doing wrong.

 

[blamocur]

It's hard for me to understand which problem you are solving -- can you post the original problem statement?

 

[topsquark]

What exactly is [imath]EL_xf(x)[/imath]? And line 3 is wrong.

-Dan

 

[BigBeachBanana]

What exactly is [imath]EL_xf(x)[/imath]?

[imath]EL_xf(x)[/imath] is the notation for elasticity, the instantaneous rate of change in percent per percent on a logarithmic scale. A common example is the price elasticity, the change in consumption of a product with respect to the change in price.
In general, it's defined as:
[math]EL_xf(x)= \frac{d\ln(f(x))}{d(\ln(x))}[/math]and of course [imath]x, f(x) >0[/imath].

 

[Deleted member 4993]

[imath]EL_xf(x)[/imath] is the notation for elasticity, the instantaneous rate of change in percent per percent on a logarithmic scale. A common example is the price elasticity, the change in consumption of a product with respect to the change in price.
In general, it's defined as:
[math]EL_xf(x)= \frac{d\ln(f(x))}{d(\ln(x))}[/math]and of course [imath]x, f(x) >0[/imath].

Learned something new here. I am trained in "mechanics". There Elasticity has a different - but strangely similar meaning. Those letters (E, L_x, etc.) is different.

Context is so important.......

 

[JeffM]

Economists frequently use a horrible notation, for example, [imath]MC(q) = \dfrac{dc}{dq}[/imath].

One reason for that is that they tend to be careless of domain and existence issues while making an assumption that is always empirically wrong and sometimes vitiating, namely that their functions are continuous and differentiable in quadrant I.

Oh, I left out the most important assumption: virtually all partials are zero, the assumption of ceteris paribus.

 

[JeffM]

Learned something new here. I am trained in "mechanics". There Elasticity has a different - but strangely similar meaning. Those letters (E, L_x, etc.) is different.

Context is so important.......

In terms of something empirically observable, price elasticity is

[math]\dfrac{\Delta q}{q} \div \dfrac{\Delta p}{p}.[/math]

 

[Deleted member 4993]

In terms of something empirically observable, price elasticity is

[math]\dfrac{\Delta q}{q} \div \dfrac{\Delta p}{p}.[/math]

I assume p is price. What is q - is it quantity?

 

[BigBeachBanana]

I assume p is price. What is q - is it quantity?

Yes, quantity demand.

 

[JeffM]

I assume p is price. What is q - is it quantity?

It is either quantity demanded or quantity supplied

 

[hajfajv]

haha this got out of hand

Could someone tell me why I get 2/y^5 book says it supposed to be just 2

 

[hajfajv]

[imath]EL_xf(x)[/imath] is the notation for elasticity, the instantaneous rate of change in percent per percent on a logarithmic scale. A common example is the price elasticity, the change in consumption of a product with respect to the change in price.
In general, it's defined as:
[math]EL_xf(x)= \frac{d\ln(f(x))}{d(\ln(x))}[/math]and of course [imath]x, f(x) >0[/imath].

Do you know everything?

 

[topsquark]

haha this got out of hand

Could someone tell me why I get 2/y^5 book says it supposed to be just 2

Look at this again. [imath]z = x^2 y^5[/imath]. What is [imath]\dfrac{ \partial }{ \partial x} z[/imath]?

-Dan

 

[hajfajv]

Look at this again. [imath]z = x^2 y^5[/imath]. What is [imath]\dfrac{ \partial }{ \partial x} z[/imath]?

-Dan

My bad I was remembering how I did the previous problem wrong, assuming all none x = 0 even if it was multiplied to an x

 

[hajfajv]

My bad I was remembering how I did the previous problem wrong, assuming all none x = 0 even if it was multiplied to an x

Thinking more about it, that would be bad

 

[topsquark]

So what do you get for [imath]\dfrac{ \partial }{ \partial x} z[/imath]?

-Dan