设f(u,v)具有二阶连续偏导数,且满足

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问题 设f(u,v)具有二阶连续偏导数,且满足

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答案[*]=yf1’+xf2’. [*]=y(yf11”+xf12”)+f2’+x(yf21"+xf22")=y2f11"+2xyf12"+x2f22"+f2’, [*]=xf1’—yf2’, [*]=x(xf11"一yf12")一f2’一y(xf21"一yf22)=x2f11"一2xyf12"+y2f22"一f2’, [*]=(x2+y2)(f11"+f22”)=x2+y2

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