1. ## 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

2. ## Re: Equalities -Need Help

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.

3. ## Re: Equalities -Need Help

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 $\displaystyle |a-b|$ is the distance between $\displaystyle a~\&~b$.
Distance is never negative.
With that in mind, which is the answer?

5. ## Re: Equalities -Need Help

Wait....not (b) .... I think its (c). Pls correct me if im wrong ((:

6. ## Re: Equalities -Need Help

Originally Posted by weijing85
Wait....not (b) .... I think its (c). Pls correct me if im
Let $\displaystyle A=\{x:-4<x<4\}~\&~B=(-\infty,-9)\cup(9,\infty)$.

What is the minimum distance between those two sets?