The two equations graphs intersect and the points where they are touching are belonging to both graphs therefore solutions for both equations.
(2) points (x,y) are
(-1,0) (-1)^2. +0^2=1; 1=1 ✔️
0=-1+1; 0=0✔️
(0, 1). (0)^2. +1^2=1; 1=1 ✔️
1=0+1; 1=1 ✔️