cho x,y thoa man: x^2+y^2= x+y .tim MIN ,MAX cua B=x-y
tim cap so nguyen (x,y) thoa man: x+y+xy=2
tim cap so nguyen (x;y) thoa man : |x+2| + (y+2)2 = 3 - |x+1|
tim x,y,z,t thoa man x^2+y^2+z^2+t^2=x(y+z+t)
tim so nguyen duong x,y thoa man : x^2=1!+2!+3!+....+y!
tim x;y;z thoa man :5x-3y/4=2z-3x/5=9y-10z/7;2y-z=132
tim x;y;z thoa man :x+3y/19=3y+9z/114=5z+15x;x+y+2z=-31
tim cap so nguyen x,y thoa man: |x+4|+|y-2|=3
Tim cac so nguyen thoa man (x+y)^2=(x-1)(y+1)
tim x,y thoa man:/x-1/+/x-2/+/y-3/+/x-4/=3