If you plug in 5 for x, the radical ends up being (5-1) which is 4. The square root of 4 is 2, and the plus/minus symbol means the possible answers are 2 OR -2. When you plug in 1 for x the radical becomes (1-1) or zero. The square root of 0 is zero, and plus/minus zero are the same. This IS NOT a function because for x=10 and x=5, there are TWO DIFFERENT y values (each “x” can only have one y in a function)