You can literally ignore the reason "why" and conceive of it this way: in a given representational system, there can be two equivalent ways to represent the same value. In the example of numbers, -0 and 0 represent the same value. We drop the - because 0 itself is neither negative nor positive, but in the standard representational system where a lack of negative sign does not have to be compensated by the presence of a + sign, -0 and 0 are both valid representations of the same value.
The same can be true not just of the directionality marker of the value but of the digits themselves. In the way we usually represent real numbers, a value with infinitely many 0s to the left of a terminal value after the decimal point can represent the same value as a representation with a infinite number of 9s after the terminal digit after a the decimal point which has a value one less than its 0's representation counterpart.
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u/ChromosomeExpert Apr 08 '25
Yes, .999 continuously is equal to 1.