Question

Which relation is a function

Answer 1

$\{(\boxed{2};\ 3);\ (1;\ 5);\ (\boxed{2};\ 7)\}-NO\\\\\{(-1;\ 5);\ (-2;\ 6);\ (-3;\ 7)\}-YES\\\\\{(\boxed{11};\ 9);\ (\boxed{11};\ 5);\ (9;\ 3)\}-NO\\\\\{(\boxed{3};\ 8);\ (0;\ 8);\ (\boxed{3};\ -2)\}-NO$