It says the ABS function will return:
x: if x is greater than or equal to 0.
-x: if x is less than 0.
This is a bit unclear! Now, I realise that if x is negative, then -x is positive, but not everyone will so this is a bit too confusing.
Why not simply say:
The abs(x) function returns the absolute value of x, that is to say it returns x without the sign.
and provide some examples :
x= 4.5 returns 4.5
x= -3.2 returns 3.2
x= 0 returns 0
Hope that can be updated.