设f(u,n)具有连续的二阶偏导数,z=f(3x+2y,y²),求2z/2x + 2²z/2x2y
问题描述:
设f(u,n)具有连续的二阶偏导数,z=f(3x+2y,y²),求2z/2x + 2²z/2x2y
答
∂z/∂x = ∂f /∂u * ∂u/∂x = 3 fu'∂²z / ∂x∂y = 3 fuu'' * ∂u/∂y + 3 fuv'' * ∂v/∂y= 3 fuu'' * 2 + 3 fuv'' * 2y= 6 fuu'' + 6...