Let R = {(P, Q) | P and Q are at the same distance from the origin} be a relation, then the equivalence class of (1, -1) is the set:
1
S = {(x, y) | x2 + y2 = 4}
2
S = {(x, y) | x2 + y2 = 2}
3
S = {(x, y) | x2 + y2 = 1}
4
S = {(x, y) | x2 + y2 = \(\sqrt2\) }