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# Maths question...help needed. PROBLEM SOLVED!

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Y = 4xz – x^4 – z^4 (Squiggly d’s btw) Dy/dx = 4z – 4x^3 Dy/dz = 4x – 4z^3 D2y/dx2 = -12x^2 D2y/dz2= -12z^2 How can I work out d2y/dxdz or d2y/dzdx which is the same thi… Read More
6y, 1m agoPosted 6 years, 1 month ago
Y = 4xz – x^4 – z^4

(Squiggly d’s btw)

Dy/dx = 4z – 4x^3

Dy/dz = 4x – 4z^3

D2y/dx2 = -12x^2

D2y/dz2= -12z^2

How can I work out d2y/dxdz or d2y/dzdx which is the same thing….?
6y, 1m agoPosted 6 years, 1 month ago
Options

(21)
#1
tree fiddy
1 Like #2
splatsplatsplat
tree fiddy

mazel tov
#3
what is z?
a constant or a function z(x) that consists of x?

edit: i think z may be a function of x and y, z(x,y)? otherwise d2y/dxdy = 0?

Edited By: mug51 on May 19, 2011 16:31
#4
#5
Rupz

not homework, just doing this for fun oO
#6
mug51
what is z?
a constant or a function z(x) that consists of x?

edit: i think z may be a function of x and y, z(x,y)? otherwise d2y/dxdy = 0?

Partial differentiation question.

Y(X,Z) = 4xz – x^4 – z^4
#7
davidbeckham187
Rupz

not homework, just doing this for fun oO

ok, let you off......geek :D
1 Like #8
Do you mean d^2y/dxdz instead of d^2y/dxdy?
#9
davidbeckham187
Rupz

not homework, just doing this for fun oO

oO......you do head wrecking math for fun ?!?!
#10
CamoChris
Do you mean d^2y/dxdz instead of d^2y/dxdy?

yes....lol
#11
CamoChris
Do you mean d^2y/dxdz instead of d^2y/dxdy?

is it 4 or -12?
1 Like #12
davidbeckham187
CamoChris
Do you mean d^2y/dxdz instead of d^2y/dxdy?

is it 4 or -12?

4, as d^2y/dxdz is d(dy/dx)/dz i.e dy/dx differentiated w.r.t z
#13
flip a coin, heads is 4 tails is -12....

its -12 as i got tails
#14
CamoChris
davidbeckham187
CamoChris
Do you mean d^2y/dxdz instead of d^2y/dxdy?

is it 4 or -12?

4, as d^2y/dxdz is d(dy/dx)/dz i.e dy/dx differentiated w.r.t z

oh alright. Thanks....!
#15
I have (4xz + 16xz^3 - 16x^4 - 16z^4)/d^2y =dxdz

Then rearranging i get (d^2y)^2/above = your equation, just squared...

So the answer I get finally, is the square root of the answer in bold at the top ;)
#16
Doesn't x = y = z = 0 solve all of those equations?
:D;)
#17
#18
Mr Weasle

Too hard. Can I stand on yours instead?
1 Like #19
To geek it up a little further, that's a smooth function on RxR and so d^2y/dxdz and d^2y/dzdx are the same.
#20
jenovat
To geek it up a little further, that's a smooth function on RxR and so d^2y/dxdz and d^2y/dzdx are the same.

ha ha lol.
#21
looking back now i feel like an idiot for posting this thread.
these are tooo easy now.
ha ha!