求答案。。。。。。。。。。。

1、F(x,y,z) = x^2 + 2y^2 + 3z^2 +xy - z - 7，F'x(2,-2,1) = 2x + y = 4 - 2 = 2；F'y(2,-2,1) = 4y + x = -8 + 2 = -6；F'z(2,-2,1) = 6z - 1 = 6 - 1 = 5；切平面方程 2( x - 2 ) - 6( y + 2 ) + 5( z - 1 ) = 0，2x - 6y + 5z - 21 = 0；2、∂z/∂x =cos(x+2y)(x)' =cos(x+2y)； ∂z/∂y = cos(x+2y)(2y)' = 2cos(x+2y)；3、5Z^4Z'x - 4x^3 + 3yZ^2 = 0，5Z^4Z'x = 4x^3 - 3yZ^2，∂z/∂x =Z'x = (4x^3 - 3yZ^2 )/5Z^4 = (4/5)x^3/Z^4 - (3/5)y/Z^25Z^4 + Z^3 + 3yZ^2Z'y = 0，3yZ^2Z'y = -5Z^4 -Z^3，∂z/∂y =Z'y = -(5/3)Z^2/y - Z/(3y) 。