Is the relation a function? (3, 6) (10, 13) (11, 1) (13, 6)

yes this is a function



The reason why is because we don't have any repeated x values. Each input (x) leads to exactly one output (y). If you plotted all the points, then you would not be able to pass a single vertical line through more than one point. So this graph passes the vertical line test.