求二阶偏导数 x^2+y^2+z^2-4z=0 求 а^2z/аx^2

z=yf(xy,2x+y),f有二阶连续偏导数,求аz/аx,аz/аy,аz/аxаy 设z=z(x,y)是方程x^2+z^2=ysin(z/x)确定的隐函数,求Z对x,y的偏导数 1.已知x,y,z满足2│x-y│+(根号2y-z)+z平方-z+(1/4)=0,求x,y,z值. x=y/z=z/3,x+y+z ＝12,求2x+3y+4z是多少, 已知x、y、z满足方程组：x+y-z=6；y+z-x=2；z+x-y=0 求x、y、z的值 x^2+y^2+z^2+4x+4y+4z+1=0,求x+y+z x^2+y^2+z^2+4x+4y+4z+1=0求x+y+z x^2+y^2+z^2+4x+4y+4z+1=0 求x+y+z x*x+y*y+2z*z-2x+4y+4z+7=0,求xyz的值 若x/2=y/3=z/4不等于0,求x+y+z/x+y-z的值 高数 求偏导数已知sinxy-2z+e^z=0,求偏z/偏x和偏z/偏y 已知x,y,z满足方程组｛x+y-z=6{y+z-x=2{z+x_y=0,求x,y,z的值