Question

evaluating expression? l4l

Answer 1

is 4 < 0?

Answer 2

Better to know how to find the answer than to know the answer.

Answer 3

\(\implies \) Better to give a way to find the answer than to give the answer.

Answer 4

+-4

Answer 5

so its the same thing with 0 it well just be 0

Answer 6

It is the same for 0 yes. As I said in your previous question

\[|a| = a \text{ if } a \ge 0\]
\[|a| = -a \text{ if } a \lt 0\]

Answer 7

ok what about -4-5

Answer 8

Sorry, was that |-4-5| ?

Answer 9

yes

Answer 10

Well, is -4-5 < 0?

Answer 11

(what does -4-5 simplify to)

Answer 12

it simplify's to -9 right so no its not greater then 0

Answer 13

So then what is |-9| ?

Answer 14

Since -9 is less than 0, then |-9| is -(-9) according to the rules we laid out before right?

Answer 15

l-9l=l9l<0 because 9 is greater

Answer 16

Sorry that's a bit confused.

Answer 17

\[|a| = a \text{ if } a \ge 0\]
Since a is -9 in this case and is not greater than or equal to 0 here we can ignore this option and look at the other.

\[|a| = -a \text{ if } a < 0\]

Since -9 is less than 0 we have that |-9| = -(-9)

So what does -(-9) simplify to?

Answer 18

@daijanik
|positive no| = the number itself
|negative no| = the number without its negative sign
so
|7| = 7
|-7| = 7
but
-|7| = -7
-|-7| = -7

hope this short and clear explanation makes things easier for you.......

Answer 19

That explanation works perfectly well until they have to solve |x - 3| = 15

Answer 20

But yes, it is a good way to think about it.

Answer 21

@polpak
let us forget n forgive ..... OK?? :))
on the way to learning, you come across many bridges/obstacles. let us not cross the bridges before they come..

since he does not have the basics, let us first concentrate on the type of problems he has to solve now
once this concept is clear and he comes to problems like you pointed out, then we provide more information/explanation to him..... :))

Answer 22

Certainly. Which was why I was agreeing with you ;p

I get annoyed when tutors give answers with no explanations. I realize you aren't the only one who does it, but it doesn't help the student any and they can just as easily get those answers from typing in their question to wolframalpha.

It's pointless for them to ask it if that's all the response they get and it wastes time and space in the question queue. So I'd rather encourage the tutors here to engage with students and try to teach them why/how they got the answer by asking questions. For those students who are only interested in getting answers it's more effective to point them to wolframalpha so that they don't continue to post the same questions here over and over again.

Although I realize some people (not you) like these students for the inflation they get on medals etc it's counter productive.

Answer 23

If u hv been going thru solutions, u will find that i also try to elicit a response first but many of them just refuse to "think" and say can u pls give detailed solution (to algebra problems especially) and do give it
But my interaction with many shows that they just want ans and no explanation!!!! You must also be facing many such students...

Answer 24

-(-9) simplfiy's to -9

Answer 25

is it -(-9) or -|-9| ????

Answer 26

No, remember when you multiply by - you change sign.
\[-(-9) = -1(-9) = (-1)(-1)9 = 9\]

Answer 27

He's going by my explanation that since -9 is less than 0:
|-9| = -(-9) = 9

Answer 28

yea thats what i ment i got it thanks so much

Answer 29

ok then as polpak pointed out...............

Answer 30

@harkirat:

I certainly see those students. And when I do, I direct them to wolframalpha.com or just ignore them. It's a waste of my time and energy to try to help people with a problem, only to have them come back 30 more times with the same problems but using different numbers each time.

Answer 31

But when I'm actually engaged with someone who is interested in learning and understanding it is just as frustrating to have a 'helpful' tutor jump in and toss out the answer with no explaination, etc.

Answer 32

yeah, there are many who just dump their entire homework on this site.......
maybe shadowfiend should look into that too...
block if they dump too many questions in a go...

Answer 33

it would be nice to have some kind of a rate-limit. But they are doing a lot of improving around here, so I can always hope ;)

Answer 34

yeah, Insha-allah (God willing)!!!

Answer 35

bye then, meet in some other question discussion then.......

Answer 36

Ok. see you around =)

Answer 37

Haha. Rate limiting is in the game plan, we just have to figure out the best way to do it!

Answer 38

We're working as fast as we can. Thanks for helping as mind-blowingly fast as you do :)

Answer 39

<3

Answer 40

good!! that will sort out the effort-shirkers who want to finish homework fast and then go to party till mid-night ....

Answer 41

yes, you guys definitely have the right idea by trying to actually teach. others definitely notice, and it helps make the site what it is. keep up the great work!

@daijanik, sorry to hijack yr question :p