hi there!(adsbygoogle = window.adsbygoogle || []).push({});

If ab > 0, then (a > 0 and b > 0) or (a < 0 and b < 0). This statment I can prove, just with the basic properties of numbers!

Then, 1[itex]/[/itex]b is defined as b[itex]^{-1}[/itex] right?

So, how does one prove that if [itex]\frac{a}{b}[/itex] > 0, then (a > 0 and b > 0) or (a < 0 and b < 0)?

Can you give me the complete proog of that? Thanks!

For example, how does one prove that if [itex]\frac{x+1}{x-1}[/itex] > 0, then

x > 1 or x < -1?

Regards,

**Physics Forums | Science Articles, Homework Help, Discussion**

Join Physics Forums Today!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

# Prove of Statement, Calculus, Basic Properties of numbers

**Physics Forums | Science Articles, Homework Help, Discussion**