[tex]1). \left \{ {{ x^{2} -5xy+6 y^{2}=0 } \atop { x^{2} + y^{2}=10 }} ight. \\ 2). \left \{ {{ \frac{4}{x+y+1}= \frac{2}{x-y+1} } \atop { \frac{x-y-1}{-1}= \frac{x+y+1}{3} }} ight. [/tex]