a)
[tex]\left \{ {{x^2+y^2=1} \atop {x+y=1}} \right. \\\left \{ {{x^2+y^2=1} \atop {y=1-x}} \right. \\\left \{ {{x^2+(1-x)^2=1} \atop {y=1-x}} \right. \\\left \{ {{x^2+1-2x+x^2=1} \atop {y=1-x}} \right. \\\left \{ {{2x^2-2x=0\ |:2} \atop {y=1-x}} \right. \\\left \{ {{x^2-x=0} \atop {y=1-x}} \right. \\\left \{ {{x(x-1)=0} \atop {y=1-x}} \right. \\\left \{ {{x=0} \atop {y=1}} \right. \vee \left \{ {{x=1} \atop {y=0}} \right.[/tex]
b)
[tex]\left \{ {{x^2+y^2=2} \atop {x-y=2}} \right. \\\left \{ {{x^2+y^2=2} \atop {y=x-2}} \right. \\\left \{ {{x^2+(x-2)^2=2} \atop {y=x-2}} \right.\\\left \{ {{x^2+x^2-4x+4=2} \atop {y=x-2}} \right.\\\left \{ {{2x^2-4x+2=0\ |:2} \atop {y=x-2}} \right.\\\left \{ {{x^2-2x+1=0} \atop {y=x-2}} \right.\\\left \{ {{(x-1)^2=0} \atop {y=x-2}} \right.\\\left \{ {{x-1=0} \atop {y=x-2}} \right.\\\left \{ {{x=1} \atop {y=-1}} \right.[/tex]
