Why the order of the coordinates does not matter when calculating length

The formula for calculating length is:


We can also write or
Why it does not matter?
Let's assume we have 2 numbers, a and b.
When we perform a subtraction:
, we get another number
When we perform another subtraction:
, we get a number

When we raise or to the power of 2, the result is the same, .

Yes i could be the length of the triangle