Sneaky Partial Derivative?

[eric_f]

I can't help but think I'm missing a key step somewhere...unless this is just a bait question, lol. Can someone check my work? You can click the small image below to enlarge it. Yes, I've triple checked that I have the correct problem from the assignment. ~Eric

 

[Steven G]

I can't help but think I'm missing a key step somewhere...unless this is just a bait question, lol. Can someone check my work? You can click the small image below to enlarge it. Yes, I've triple checked that I have the correct problem from the assignment. ~Eric

View attachment 4842

Your work is flawless. My concern is that you questioned it. If df/dx = any constant then d^2f/(dydx) = (d/dy)(df/dx)==(d/dy)(constant) = 0

 

[eric_f]

Thanks! I thought I was going crazy, but it turns out I've been at it too long today already...

 

[Steven G]

Thanks! I thought I was going crazy, but it turns out I've been at it too long today already...

You might still be going crazy. I did not have any trouble checking your work and I AM crazy!
Just glad that you understand the work!

 

[HallsofIvy]

Well, one obvious flaw is that you have \(\displaystyle \frac{\partial^2 f}{\partial y\partial x}(2, 1, 2)= (0, 0, 0)\).

Since f is "real valued" function, so are all of its derivatives- you should have just "0" rather than "(0, 0, 0)".

(I acknowledge that this was probably just a typo.)

 

[Steven G]

Well, one obvious flaw is that you have \(\displaystyle \frac{\partial^2 f}{\partial y\partial x}(2, 1, 2)= (0, 0, 0)\).

Since f is "real valued" function, so are all of its derivatives- you should have just "0" rather than "(0, 0, 0)".

(I acknowledge that this was probably just a typo.)

Ouch! I knew something look wrong when I saw (0,0,0) but I did not see what you thought. Darn! Thanks for pointing this out!

 

[Deleted member 4993]

I received this PM from eric_f today:

Attention! If you still dont know about wide range of computers, phones, laptops, photo cameras, video cameras, clothes, jewelry, goods for sport, fishing, hunting, cars, motorcycles and other branches cheaper than on eBay. Go to
Anybody else?

Me too ... so I banned him for spamming...

 

[Ishuda]

I received this PM from eric_f today:

Attention! If you still dont know about wide range of computers, phones, laptops, photo cameras, video cameras, clothes, jewelry, goods for sport, fishing, hunting, cars, motorcycles and other branches cheaper than on eBay. ...

Anybody else?

Nope {I removed the link}

 

[lookagain]

I received this PM from eric_f today:

Attention! If you still dont know about wide range of computers, phones, laptops, photo cameras, video cameras, clothes, jewelry, goods for sport, fishing, hunting, cars, motorcycles and other branches cheaper than on eBay. Go to
Anybody else?

Yes, I did.

 

[jonah2.0]

Sneaky Partial Derivative and ad

DISCLAIMER: Beer soaked rambling/opinion/observation/reckoning ahead. Read at your own risk. Not to be taken seriously. In no event shall the wandering math knight-errant Sir jonah in his inebriated state be liable to anyone for special, collateral, incidental, or consequential damages in connection with or arising out of the use of his beer (and tequila) powered views.

I received this PM from eric_f today:

Attention! If you still dont know about wide range of computers, phones, laptops, photo cameras, video cameras, clothes, jewelry, goods for sport, fishing, hunting, cars, motorcycles and other branches cheaper than on eBay. Go to
Anybody else?

Yeah, me too.
Love that guy.
He's just trying to make extra money.
Nothing wrong with that.
It's beautiful.