z=ye^-x的二阶偏导数等于多少
z的一阶偏导数为:
∂z/∂x = -y*e^-x
∂z/∂y = e^-x
因此,z的二阶偏导数为:
∂²z/∂x² = -∂/∂x (y*e^-x)
= -(-y*e^-x)
= y*e^-x
∂²z/∂y² = 0
∂²z/∂x∂y = ∂/∂y (-y*e^-x)
= -e^-x
因此,z=y*e^-x的二阶偏导数为:
∂²z/∂x² = y*e^-x
∂²z/∂y² = 0
∂²z/∂x∂y = -e^-x
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