Show that `-a`is not the inverse of `a in N`for the addition operation + on N and `1/a` is not the inverse of `a in N`for multiplication operation `xx`on N, for `a!=1`.

Explanation

Addition

`a in N`

Hence, a is a natural number (i.e. positive number 1, 2, 3, ...)

So, `-a` will be negative

Hence `-a` is not a natural number
`-a in N`
So, `-a` is not the inverse of `a` for addition on `N`.


Multiplication
`a in N`

Hence, a is a natural number (i.e. positive number `1, 2, 3, ...`)

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