Okay.Originally Posted bybraddy

If,

There exists preciesly one such number such as because the real numbers form a group under addition.

Thus,

Since addition is associative we have,

Thus,

Since,

is an identity element we have,

Since, it is an element of the real numbers under multiplication and form a group. Thus, there exist a unique, such as, .

Thus,

Since, multiplication is associative we have,

Thus,

Since 1 is the multiplicative identity element we have,