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    Maths question...help needed. PROBLEM SOLVED!

    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….?

    21 Comments

    tree fiddy

    Original Poster

    splatsplatsplat

    tree fiddy



    mazel tov

    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" 19th May 2011

    do your own homework!

    Original Poster

    Rupz

    do your own homework!



    not homework, just doing this for fun oO

    Original Poster

    mug51

    what is z?a constant or a function z(x) that consists of x?edit: i think … 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

    davidbeckham187

    not homework, just doing this for fun oO



    ok, let you off......geek

    Do you mean d^2y/dxdz instead of d^2y/dxdy?

    davidbeckham187

    not homework, just doing this for fun oO




    oO......you do head wrecking math for fun ?!?!

    Original Poster

    CamoChris

    Do you mean d^2y/dxdz instead of d^2y/dxdy?



    yes....lol

    Original Poster

    CamoChris

    Do you mean d^2y/dxdz instead of d^2y/dxdy?



    is it 4 or -12?

    davidbeckham187

    is it 4 or -12?


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

    flip a coin, heads is 4 tails is -12....


    its -12 as i got tails

    Original Poster

    CamoChris

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



    oh alright. Thanks....!

    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

    Doesn't x = y = z = 0 solve all of those equations?

    Try standing on your head

    Mr Weasle

    Try standing on your head



    Too hard. Can I stand on yours instead?

    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.

    Original Poster

    jenovat

    To geek it up a little further, that's a smooth function on RxR and so … 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.
    stop looking at my threads!

    Original Poster

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