x^2+y^2=58
x-y=4
x^2+y^2=58
x=4+y
(4+y)^2+y^2=58
16+8y+y^2+y^2=58
16+8y+2y^2=58
16+8y+2y^2-58=0
2(8+4y+y^2-29)=0
2(-21+4y+y^2)=0
2(y^2+4y-21)=0
2(y^2+7y-3y-21)=0
2[y•(y+7)-3(y+7)]=0
2(y-3)•(y+7)=0
(y-3)•(y+7)=0
y-3=0
y+7=0
y=3
y=-7
x=4+7
x=4-7
x=7
x=-3
(x indice 1;y indice 1)= (7;3)
(x indice 2;y indice 2)=(-3;-7)
