这道高数题怎么做
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解:
令:F(x,y,z)=z(e^z)-x(e^x)-y(e^y)
根据隐函数求导公式:
z'x=-F'x/F'z = [(e^x)+x(e^x)]/[(e^z)+z(e^z)]
z'y=-F'y/F'z = [(e^y)+y(e^y)]/[(e^z)+z(e^z)]
du
=(∂u/∂x)dx+(∂u/∂y)dy
∂u/∂x
=[(1+z'x)(y+z)-z'x·(x+z)]/(y+z)²
=[(y+z)+z'x(y+z-x-z)]/(y+z)²
=[(y+z)+z'x(y-x)]/(y+z)²
=[1/(y+z)]+[z'x(y-x)/(y+z)²]
∴选C
令:F(x,y,z)=z(e^z)-x(e^x)-y(e^y)
根据隐函数求导公式:
z'x=-F'x/F'z = [(e^x)+x(e^x)]/[(e^z)+z(e^z)]
z'y=-F'y/F'z = [(e^y)+y(e^y)]/[(e^z)+z(e^z)]
du
=(∂u/∂x)dx+(∂u/∂y)dy
∂u/∂x
=[(1+z'x)(y+z)-z'x·(x+z)]/(y+z)²
=[(y+z)+z'x(y+z-x-z)]/(y+z)²
=[(y+z)+z'x(y-x)]/(y+z)²
=[1/(y+z)]+[z'x(y-x)/(y+z)²]
∴选C
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