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