函數u=ln(x+y+z)在點M(1,2,-2)處的梯度是多少

函數u=ln(x+y+z)在點M(1,2,-2)處的梯度是多少

梯度=(∂;u/∂;x,∂;u/∂;y,∂;u/∂;z)
∂;u/∂;x=1/(x+y+z),∂;u/∂;y=1/(x+y+z),∂;u/∂;z=1/(x+y+z),
u點M(1,2,-2)處的梯度:(1,1,1).