1)[tex]\left \{ {{\frac{1}{x}-\frac{1}{y} =3 } \atop {x^{2}+2y^{2} =5 }} \right. => \left \{ {{-\frac{1}{1}-\frac{1}{2}=3 } \atop {(-1)^{2}+2*2^{2}=5 }} \right. =>\left \{ {{-1,5=3} \atop {9=5}} \right. => (-)[/tex]
2)[tex]\left \{ {{x^{2}+3y^{2}=13 } \atop {x+3y=5}} \right. =>\left \{ {{(-1)^{2}+3*2^{2}=13 } \atop {-1+3*2=5}} \right. =>\left \{ {{13=13} \atop {5=5}} \right. =>(+)[/tex]
3)[tex]\left \{ {{3x+2y=1} \atop {x^{2}-y^{2}=-4 }} \right. =>\left \{ {{3*(-1)+2*2=1} \atop {(-1)^{2} -2^{2}=-4 }} \right. =>\left \{ {{1=1} \atop {-3=-4}} \right. =>(-)[/tex]
4)[tex]\left \{ {{x-y=1} \atop {(x-1)(y+2)=2}} \right. =>\left \{ {{-1-2=1} \atop {(-1-1)(2+2)=2}} \right. =>\left \{ {{-3=1} \atop {-8=2}} \right. =>(-)[/tex]
Ответ:2