I can give you some viewpoits about it ,you can expand it.
In the math matic,we always start with definitions .what do you mean by one what do you mean by two?what do you mean by plus?what do you mean by equal?once you get definitions done the answer is obvious.using the standard of one ,two,plus and equal,then by the definitions one plus one equals two.here ,what we mean by "two" is just one more one.if there is a formula that says otherwise ,we know it use the different definitions from its ordinary meaning.
that's all ,hope it can help you.
