e的y次方+xy=e 求二阶导数

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e的y次方+xy=e 求二阶导数

e的y次方+xy=e 求二阶导数
e的y次方+xy=e 求二阶导数

e的y次方+xy=e 求二阶导数
求二阶真的麻烦,容易出错,只好详细求了.
求二价y''时那个y'就代回一阶导数的答案便可以了.

方程两边同时对x求导得e^y*(dy/dx)+y+x*(dy/dx)=0.解得dy/dx=(-y)/(e^y+x).对上述方程两边再x求导得e^y*(dy/dx)^2+e^y*(d^2y)/dx^2+dy/dx+x*(d^2y)/dx^2+dy/dx=0.解得d^2y/dx^2=(y^2-2xy-2ye^y)/(e^y+x)^3

e^y + x y = e
e^y * y' + (y+x y') = 0, 即 y' * (e^y+x) = -y @
=> y' = - y / (e^y + x)
@ 两端再对x 求导:
y ‘’ * (e ^y + x) + y’ * (e^y * y’ + 1) = - y’
=> y ‘’ = - y’ * (e^y * y’ ...

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e^y + x y = e
e^y * y' + (y+x y') = 0, 即 y' * (e^y+x) = -y @
=> y' = - y / (e^y + x)
@ 两端再对x 求导:
y ‘’ * (e ^y + x) + y’ * (e^y * y’ + 1) = - y’
=> y ‘’ = - y’ * (e^y * y’ + 2) / (e ^y + x)
代入 y’, 得:
y ‘’ = y ( -y e^y + 2 e^y + 2x) / (e^y + x) ³

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