Z=x/(x^2+y^2)+y/(x+y)求x的偏导,y的偏导,先x后y的二阶偏导
设函数z=yf(x/y)+xg(y/x),求 X×(z的x的二阶偏导)+Y×(z的x,y的混合偏导)
x y z x+y--- = --- = ---- ----y+Z z+x x+y ,求 z 的值 .求 x+y----
已知x/z=ln(z/y),求z对x和y的偏导.
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
{(z+y)(x-y)-(x-y)的2次方+2y(x-y)}除以4y
若x-y=6,xy=-8,求代数式(x+y+z)²+(x-y-z)(x-y+z)-2·z(x+y)的值
z=f(x^2-y^2,xy),求z关于y的偏导
已知x=2,x+y+z=-2.8,求x^2(-y-z)-3.2x(z+y)的值
f(x,y)=exp(-(x+y)) x>0 y>0 求Z=(X+Y)/2的概率密度.
Z=f(x+y,f(x,y)) 求它的二阶偏导 先对x ,在对Y 求偏导~
X:Y:Z=2:3:4,求x-2y+3x分之x+y+z的值
若X:Y:Z=2:3:4求X+Y+Z/X-2Y+3X的值