Question

tim x va y thoa man: x^2 - xy -2y^2 - 1 = 0

Answer 1

=>x^2-y^2-xy-y^2=1

=>(x-y)(x+y)-y(x+y)=1

=>(x+y)*(x-2y)=1

=>(x+y;x-2y)=(1;1) hoặc (x+y;x-2y)=(-1;-1)

=>(x,y)=(1;0) hoặc (x,y)=(-1;0)