Cho x y z la cac so huu ti doi mot khac nhau va khac khong thoa man x+1/y=y+1/z=z+1/x Chung minh xyz=1 hoac xyz=-1
Cho x,y,z khac nhau va :1/x+1/y+1/z=1/x+y+z
CMR trong 3 so x,y,z co it nhat 1 cap so doi nhau
Cho x,y,z la cac so nguyen duong thoa man 1/x + 1/y + 1/z = 2015.
Tim GTLN cua bieu thuc P=x+y/x^2+y^2 + y+z/y^2+z^2 + z+x/z^2+x^2
cho x,y,z thuoc Q va doi mot khac nhau. cmr 1/ (x-y)^2+1/(y-z)^2+1/(z-x)^2 la binh phuong cua 1 so huu ti
Cho x,y,z la cac so thuc khac 0. Thoa man : z2+z(xy-xz-yz)=0
Chung minh rang x2+(x+2y-z)2 / y2+(2x+y-z)2 = x+2y-z / 2x+y-z
cm trong 3 so x,y,z ton tai 1 so bang tong 2 so con lai biet
x.(y-z)^2+y.(x-z)^2+z.(x-y)^2-x^3-y^3-z^3+4xyz=0
cho 3 so nguyen x,y,z thoa man x+y+z=0 chung minh rang x^3+y^3+z^3= 3xyz
chung minh khong ton tai 3 so nguyen x y z sao cho x^2 - 4yz = 23
cho x,y,z>0 thoa man x+y+z<=1 chung minh rang 17(x+y+z)+2(1/x+1/y+1/z)=>35