Equalities -Need Help

• February 3rd 2013, 11:16 PM
weijing85
Equalities -Need Help
Hi,

I'm curious about the question below. I felt that answer should be (a). Anyone knows?

If |a|<4 and |b|>9, then the best we can say about |a-b| is that?
(a) |a-b|<-5
(b) |a-b| > 5
(c) |a-b| <5
(d) |a-b| >13

weijing
• February 4th 2013, 01:43 AM
earboth
Re: Equalities -Need Help
Quote:

Originally Posted by weijing85
Hi,

I'm curious about the question below. I felt that answer should be (a). Anyone knows?

If |a|<4 and |b|>9, then the best we can say about |a-b| is that?
(a) |a-b|<-5
(b) |a-b| > 5
(c) |a-b| <5
(d) |a-b| >13

weijing

An absolute value is allways positive or zero. So a) is definitely not a solution to your question.

To find the answer to the question use the numberline.
• February 4th 2013, 04:03 AM
Plato
Re: Equalities -Need Help
Quote:

Originally Posted by weijing85
If |a|<4 and |b|>9, then the best we can say about |a-b| is that?
(a) |a-b|<-5 (b) |a-b| > 5 (c) |a-b| <5 (d) |a-b| >13

You have been told that it cannot be a).

Recall that $|a-b|$ is the distance between $a~\&~b$.
Distance is never negative.
With that in mind, which is the answer?
• February 4th 2013, 05:25 AM
weijing85
Re: Equalities -Need Help
• February 4th 2013, 05:25 AM
weijing85
Re: Equalities -Need Help
Wait....not (b) .... I think its (c). Pls correct me if im wrong ((:
• February 4th 2013, 06:30 AM
Plato
Re: Equalities -Need Help
Quote:

Originally Posted by weijing85
Wait....not (b) .... I think its (c). Pls correct me if im

Let $A=\{x:-4.

What is the minimum distance between those two sets?