Note that to show there is a unique object with a certain
Chapter 4, Problem 4.296(choose chapter or problem)
Note that to show there is a unique object with a certain property, show that (1) there is an object with the property and (2) if objects A and B have the property, then A = B. Prove that there is at most one real number b with the property that br =r for all real numbers r. (Such a number is called a multiplicative identity.)
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