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设函数z=f(u,v)具有二阶连续偏导数,z=f(x-y,y/x),求a^2z/axay

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设函数z=f(u,v)具有二阶连续偏导数,z=f(x-y,y/x),求a^2z/axay
设函数z=f(u,v)具有二阶连续偏导数,z=f(x-y,y/x),求a^2z/axay
令u=x-y,v=y/x
az/ax=az/au×au/ax+az/av×av/ax=fu-y/x^2×fv
a^2z/axay=a(az/ax)/ay=a(fu-y/x^2×fv)/ay=a(fu)/ay-a(y/x^2×fv)/ay=a(fu)/ay-1/x^2×fv-y/x^2×a(fv)/ay
a(fu)/ay=a(fu)/au×au/ay+a(fu)/av×av/ay=-fuu+1/x×fuv
a(fv)/ay=a(fv)/au×au/ay+a(fv)/av×av/ay=-fvu+1/x×fvv
回代,a^2z/axay=a(fu)/ay-1/x^2×fv-y/x^2×a(fv)/ay
=-fuu+1/x×fuv-1/x^2×fv-y/x^2×(-fvu+1/x×fvv)
=-fuu+(x+y)/x^2×fuv-y/x^3×fvv-1/x^2×fv