but isn't the square root of 4 always 2, not -2? For it to be -2 doesn't it have to be the square root of -4?Realised it doesn't let you do square root of -4

2) For every value of x there is only one value of y. In other words, you can't have two buildings on the same spot. This means y = x is a function, but y - va is not. Why? Let's find the value of r2 and vr at x = 4. For the function y = y = 16 at & = 4. However, for y - VI, y can be either +2 or -2 at 1 = 4 At r = 4 there are two possible values of y for the function y = Vz, but only one value for y for the function y - 1 . In other words, VI is ambiguous between two possible numbers, and 12 is not. That's why I' is a function and VI is not. Pictorially, this is a function: If