Homepage Solution manuals Terence Tao Analysis I Exercise 5.4.1 (Basic properties of positive reals)

Exercise 5.4.1 (Basic properties of positive reals)

Prove Proposition 5.4.4.

Proposition 5.4.4. For every real number x, exactly one of the following three statements is true: (a) x is zero; (b) x is positive; (c) x is negative. A real number x is negative if and only if x is positive. If x and y are positive, then so are x + y and xy.