timx,y thuoc z thoa x^2+xy+y^2=x^2y^2
tim x,y thuoc z thoa 2(x^2+y^2)=1978
tim x va y thoa man: x^2 - xy -2y^2 - 1 = 0
tim x y thuoc z biet (x+y).2=xy
tim cac gia tri x y thoa man
a,(x^2-1)(x^2-16)<0 va x thuoc Z
B,1/x-y/8=1/16 va x y thuoc N
tim cac so x,y thoa man :2x^2+y^2-2y=2(xy-1)
Tim cac gia tri x, y thoa man:
a, ( x2 - 1 ) ( x2 - 16 ) < 0 ca x thuoc z
b, 1/x - y/8 = 1/16 va x, y thuoc N
c, | x+1 | + | x+2 | + | x+3 | = x
tìm x,y thuoc z;
a) x^2-2y =5-xy+2x
cho cac so x,y,z va x+y+z khac 0 thoa man dieu kien
\(\frac{x+2y}{x+2y-z}+\frac{y+2z}{y+2z-x}+\frac{z+2x}{z+2x-+y}\)
tinh gt bieu thuc \(T=\frac{x^2+y^2}{xy}+\frac{y^2+z^2}{yz}+\frac{z^2+x^2}{zx}\)