x>0,y>0,z>0,x^2+xy+y^2=49,y^2+yz+z^2+36,z^2+xz+x^2=25,求x+y+z少年科技大大天才杨仲侠试题

若xy-z不等于0,且(y+x)/x=(z+x)/y=(y+x)/z,求[(y+z)(z+x)(x+y)]/xyz的值? 若xy-z=0,且(y+x)/x=(z+x)/y=(y+x)/z,求[(y+z)(z+x)(x+y)]/xyz的值? 若|x-3|+|y+2|+|2z+1|=0,求(xy-yz)(y-x+z) 已知x>0,y>0,z>0,证明x^3/(x+y)+y^3/(y+z)+z^3/(z+x)≥(xy+xz+yz)/2 已知方程组x+2y-z=0,2x-y+8z=0,求x*x+y*y+z*z/xy+yz的值 已知x,y,z∈（0,+∞）求证：√x^+xy+y^+√y^+yz+z^+√z^+zx+x^＞＝3/2(x+y+z ) 已知3x－y+2z=x+2y+3z=0,求（3x^－xy+2y^)/(2x^+4xy+y^)值? xy-2x+y-z-2=0求导 已知0.5|x-y|+√(2y+z)+(z^2-z+0.25)=0,则z/xy的值是 已知2x-3y-z=0,x+3y-14z=0(z≠0),求x^2+3xy／y^2+z^2 已知2x-3y-z=0 x+3y-14z=0(z≠0) 求x^+3xy/y^2+z^ 实数x,y,z满足x=y+根号2,2xy+2*根号2*z*z+1=0,则x+y+z等于多少这是道奥赛题, 已知x,y,z>0 求证:xy(x+y)+yz(y+z)+zx(z+x)>=6xyz 已知x>0,y>0,z>0,求证：√（x^2+xy+y^2)+√（y^2+yz+z^2)>x+y+z 已知｛X-3Y+7z=0,x-2y+4Z (xy不等于0）.求X:Y:ZX-2Y+4Z=0 已知：x^2/(z+y)+y^2/(x+z)+z^2/(x+y)=0,求x/(z+y)+y/(x+z)+z/(x+y)的值. x^2/(z+y)+y^2/(x+z)+z^2/(x+y)=0,求x/(z+y)+y/(x+z)+z/(x+y)的值 设函数z=z(x,y)由方程e^(-xy)-2z+e^z=0确定,求z/x,z/y