# Math proof help

• October 7th 2009, 01:57 PM
jujab
Math proof help
This is probably terribly easy for most of you, but I am stuck on a proof, maybe someone could help me!

Prove: a,b are R. If a<b, then -b<-a.

Would I use the additive inverse here?
l
• October 7th 2009, 02:03 PM
HallsofIvy
Quote:

Originally Posted by jujab
This is probably terribly easy for most of you, but I am stuck on a proof, maybe someone could help me!

Prove: a,b are R. If a<b, then -b<-a.

Would I use the additive inverse here?
l

I assume you mean the fact that a+ (-a)= 0. Yes, add a+ b to both sides of the inequality.
• October 7th 2009, 02:51 PM
Matt Westwood
Quote:

Originally Posted by HallsofIvy
I assume you mean the fact that a+ (-a)= 0. Yes, add a+ b to both sides of the inequality.

Do you mean add $-(a+b)$ to both sides of the inequality?