Discussion about math, puzzles, games and fun.   Useful symbols: ÷ × ½ √ ∞ ≠ ≤ ≥ ≈ ⇒ ± ∈ Δ θ ∴ ∑ ∫  π  -¹ ² ³ °

You are not logged in.

## #1 2017-01-24 21:35:38

Hannibal lecter
Member
Registered: 2016-02-11
Posts: 225
Website

### HI please solve this absolute value equation with interval notation ..

Hi, please solve this for me I'm in hurry .....

Last edited by Hannibal lecter (2017-01-24 21:40:06)

Wisdom is a tree which grows in the heart and fruits on the tongue

Offline

## #2 2017-01-25 03:24:05

bobbym
bumpkin
From: Bumpkinland
Registered: 2009-04-12
Posts: 109,606

### Re: HI please solve this absolute value equation with interval notation ..

Hi;

Two of my favorite places to go when I need to look like I know something about inequalities and lots more too.

http://www.mathsisfun.com/algebra/inequ … lving.html

http://www.purplemath.com/modules/ineqrtnl.htm

In mathematics, you don't understand things. You just get used to them.
If it ain't broke, fix it until it is.
Always satisfy the Prime Directive of getting the right answer above all else.

Offline

## #3 2017-01-25 08:00:04

Hannibal lecter
Member
Registered: 2016-02-11
Posts: 225
Website

### Re: HI please solve this absolute value equation with interval notation ..

Wisdom is a tree which grows in the heart and fruits on the tongue

Offline

## #4 2017-01-25 09:17:39

bobbym
bumpkin
From: Bumpkinland
Registered: 2009-04-12
Posts: 109,606

### Re: HI please solve this absolute value equation with interval notation ..

Hi;

I am getting -2 <= x <= 1 and  x > 3

In mathematics, you don't understand things. You just get used to them.
If it ain't broke, fix it until it is.
Always satisfy the Prime Directive of getting the right answer above all else.

Offline

## #5 2017-01-25 10:15:16

Hannibal lecter
Member
Registered: 2016-02-11
Posts: 225
Website

### Re: HI please solve this absolute value equation with interval notation ..

I got this question in the exam and please see this picture it was my solution I know it is wrong ..

because I forget to take the intersection between [1,∞) and [-2,∞) which will became (-∞,-2] and (-∞,1] {because there is a number which is "2" didn't make the inequality Satisfied that I found it bewteen -2 and 3, so I flip up these two Intervals then the inetersection will be[-2,1]  ) and that is what I do always

but I forget to do that and just put the (3,∞)

the question was from 10 marks  and the teacher give me 1! just 1 mark ,,,  do I deserve this???? I just want to know that if not, what do I deserve??

Last edited by Hannibal lecter (2017-01-25 10:15:52)

Wisdom is a tree which grows in the heart and fruits on the tongue

Offline

## #6 2017-01-25 11:51:16

bobbym
bumpkin
From: Bumpkinland
Registered: 2009-04-12
Posts: 109,606

### Re: HI please solve this absolute value equation with interval notation ..

Hi;

2) I am confused why you asked me for the answer when you knew how to do it?

3) How much should be deducted for your answer which was incomplete? How much partial credit is due you?

1 and 2, only you know the answer to. For 3, I do have an opinion. I do not like the concept of partial credit. In my day, you would have got a 0 for that answer. Back then, teachers even graded you on penmanship and grammar for a math question! They might flunk you for a spelling error or a run-on sentence. I did not capitalize an a on a final in chemistry and got -2 for that and failed to win the science award. A 98 was not good enough because my rival got 100.

But that was then and this is now. I would have given you +5 for your answer.

what do I deserve?

This question never applies to the real world. I suggest you never use it or even think about it again. We never get what we deserve here on Earth. It is the most unfair place ever constructed. But that works to our advantage too, the guilty do not get what they deserve either.

So, I would go against my prejudice towards partial credit and give you 5 for that answer. Back in my day, teachers sometimes gave you a break when you were polite, courteous and a good student. If you were an annoying little weasel they were not inclined to be generous.

In mathematics, you don't understand things. You just get used to them.
If it ain't broke, fix it until it is.
Always satisfy the Prime Directive of getting the right answer above all else.

Offline

## #7 2017-01-25 12:10:03

Hannibal lecter
Member
Registered: 2016-02-11
Posts: 225
Website

### Re: HI please solve this absolute value equation with interval notation ..

yes I'm saying that ,
and I asked you to solve it because the teacher don't have a constant solution for this question!
I saw a student got 10 marks from 10 ( it is mean his answer if full Correct)
but his solution was wrong! it was (-∞,1] U (3,∞) !! and not just him there was some of them .... !
they had 10 marks and me just 1!

cause I use my own way when I answer inequalities like these, my teacher his way to solve is complicated and sometimes be fully wrong!
he just give us 3 example in the copybook and it was in a wrong answer! how can I use his way that I don't like it and very complicated ...

his important thing is the student use his way and he will give a full mark or 9 or 8 !!!

and me he give me just 1

3) How much should be deducted for your answer which was incomplete? How much partial credit is due you?

I don't really know how much but what I know I don't deserve 1! what make me angry is he did that deliberately!

and I know but he use partial credit , that is his way and he must use his way correctly without injustice

Wisdom is a tree which grows in the heart and fruits on the tongue

Offline

## #8 2017-01-25 12:20:00

bobbym
bumpkin
From: Bumpkinland
Registered: 2009-04-12
Posts: 109,606

### Re: HI please solve this absolute value equation with interval notation ..

Now we are getting to the meat of the problem.

his important thing is the student use his way and he will give a full mark or 9 or 8 !

Colonel Erich (Von Hitler ) Anderson once told me this:

In this place there are 4 ways of doing things, the right way, the wrong way, the military way and my way. In this place you will do things my way.

He meant it too. Till this day, I will kill him on sight.
There is a rule in life, it is this: When in Rome do as the Romans do. I am afraid you had better do it his way else pay the price for your resistance.

In mathematics, you don't understand things. You just get used to them.
If it ain't broke, fix it until it is.
Always satisfy the Prime Directive of getting the right answer above all else.

Offline

## #9 2017-01-25 12:40:24

Hannibal lecter
Member
Registered: 2016-02-11
Posts: 225
Website

### Re: HI please solve this absolute value equation with interval notation ..

thank you .....

I really don't want to use a wrong way I want to do math in neat way and feeling good not like this
and the problem is : it is not just this problem I had with him.... all student don't have a mark up to 27,,  the exam is from 50 marks

the top of us is 27 and me 24 the remain of the student is under 24 .....
it is not the only question ,, everywhere in my paper he put a 1 or 3 I don't know why he is doing that ... anyway thank you very much for your answers and helping ....

I have this question to it was too from the exam : f(x) = x^3 + 1, x ≠0  and k^2 + 3k-3  , x=0
x continuous at x =0
what is the k value ??

lim R.H.S = lim L.HS
then
limx->0    x^3 +1 = limx->0      k^2 + 3k -3
.
.
. k value = {-1,4}

is that right?

Wisdom is a tree which grows in the heart and fruits on the tongue

Offline

## #10 2017-01-25 12:51:12

bobbym
bumpkin
From: Bumpkinland
Registered: 2009-04-12
Posts: 109,606

### Re: HI please solve this absolute value equation with interval notation ..

There is a simple way to get around that. Learn to do the problems two ways. For his tests use his way, for the real world use the right way. You do not know it yet but the whole world is already doing that!

to find k?

In mathematics, you don't understand things. You just get used to them.
If it ain't broke, fix it until it is.
Always satisfy the Prime Directive of getting the right answer above all else.

Offline

## #11 2017-01-25 12:57:03

Hannibal lecter
Member
Registered: 2016-02-11
Posts: 225
Website

### Re: HI please solve this absolute value equation with interval notation ..

yesss but that what my sol :

im R.H.S = lim L.HS
then
limx->0    x^3 +1 = limx->0      k^2 + 3k -3
.
.
. k value = {-1,4}

is that right?

............................................... so I'm not sure, but the teacher said it is wrong cause you must take just (  k^2 + 3k -3=0)
then find it , is that  the right ?? or what....

Wisdom is a tree which grows in the heart and fruits on the tongue

Offline

## #12 2017-01-25 12:58:21

bobbym
bumpkin
From: Bumpkinland
Registered: 2009-04-12
Posts: 109,606

### Re: HI please solve this absolute value equation with interval notation ..

What does the LHS equal?

In mathematics, you don't understand things. You just get used to them.
If it ain't broke, fix it until it is.
Always satisfy the Prime Directive of getting the right answer above all else.

Offline

## #13 2017-01-25 13:03:38

Hannibal lecter
Member
Registered: 2016-02-11
Posts: 225
Website

### Re: HI please solve this absolute value equation with interval notation ..

0 + 1 = 1

it is 1

Wisdom is a tree which grows in the heart and fruits on the tongue

Offline

## #14 2017-01-25 13:05:04

bobbym
bumpkin
From: Bumpkinland
Registered: 2009-04-12
Posts: 109,606

### Re: HI please solve this absolute value equation with interval notation ..

And what is the RHS?

In mathematics, you don't understand things. You just get used to them.
If it ain't broke, fix it until it is.
Always satisfy the Prime Directive of getting the right answer above all else.

Offline

## #15 2017-01-25 13:06:39

Hannibal lecter
Member
Registered: 2016-02-11
Posts: 225
Website

### Re: HI please solve this absolute value equation with interval notation ..

it is the same k^2 + 3k -3

Wisdom is a tree which grows in the heart and fruits on the tongue

Offline

## #16 2017-01-25 13:08:14

bobbym
bumpkin
From: Bumpkinland
Registered: 2009-04-12
Posts: 109,606

### Re: HI please solve this absolute value equation with interval notation ..

So you have the equation:

1 = k^2 + 3k -3

Subtract 1 from both sides:

0 = k^2 + 3k - 4

Can you solve that?

In mathematics, you don't understand things. You just get used to them.
If it ain't broke, fix it until it is.
Always satisfy the Prime Directive of getting the right answer above all else.

Offline

## #17 2017-01-25 13:12:36

Hannibal lecter
Member
Registered: 2016-02-11
Posts: 225
Website

### Re: HI please solve this absolute value equation with interval notation ..

yes it is k^2 -k + 4 k - 4 = 0
(k-1) (K=4) = 0
k=1
k=-4
set is {-4,1}

it is the same sorry I write to you -1 and 4 ,,,  but in exam I write it correct like that ....

so it right?

Wisdom is a tree which grows in the heart and fruits on the tongue

Offline

## #18 2017-01-25 13:16:35

bobbym
bumpkin
From: Bumpkinland
Registered: 2009-04-12
Posts: 109,606

### Re: HI please solve this absolute value equation with interval notation ..

Yes, as far as I know. That is how I would do the problem.

In mathematics, you don't understand things. You just get used to them.
If it ain't broke, fix it until it is.
Always satisfy the Prime Directive of getting the right answer above all else.

Offline

## #19 2017-01-25 13:17:57

Hannibal lecter
Member
Registered: 2016-02-11
Posts: 225
Website

### Re: HI please solve this absolute value equation with interval notation ..

but he say we can't take the L.HS cause the f(x) = x+1 , x ≠ 0,
because x  ≠ 0, we just use the R.H.S

is he wrong?

Wisdom is a tree which grows in the heart and fruits on the tongue

Offline

## #20 2017-01-25 13:21:43

bobbym
bumpkin
From: Bumpkinland
Registered: 2009-04-12
Posts: 109,606

### Re: HI please solve this absolute value equation with interval notation ..

Is he saying the limit of the LHS is not 1 because x does not equal 0?

In mathematics, you don't understand things. You just get used to them.
If it ain't broke, fix it until it is.
Always satisfy the Prime Directive of getting the right answer above all else.

Offline

## #21 2017-01-25 13:24:33

Hannibal lecter
Member
Registered: 2016-02-11
Posts: 225
Website

### Re: HI please solve this absolute value equation with interval notation ..

I don't understand

and he didn't say that,

Wisdom is a tree which grows in the heart and fruits on the tongue

Offline

## #22 2017-01-25 13:27:18

bobbym
bumpkin
From: Bumpkinland
Registered: 2009-04-12
Posts: 109,606

### Re: HI please solve this absolute value equation with interval notation ..

Then why does he ignore the LHS?

In mathematics, you don't understand things. You just get used to them.
If it ain't broke, fix it until it is.
Always satisfy the Prime Directive of getting the right answer above all else.

Offline

## #23 2017-01-25 13:31:04

Hannibal lecter
Member
Registered: 2016-02-11
Posts: 225
Website

### Re: HI please solve this absolute value equation with interval notation ..

cause he told us when you see x  ≠ 0 , you ignore the equation while you find k value

can you give me justification SO I can talk to him cause this question is from 10 mark too

at least I can take this 10 marks cause he give me 0

Wisdom is a tree which grows in the heart and fruits on the tongue

Offline

## #24 2017-01-25 13:33:50

bobbym
bumpkin
From: Bumpkinland
Registered: 2009-04-12
Posts: 109,606

### Re: HI please solve this absolute value equation with interval notation ..

I see no reason why you can not evaluate the limit of the LHS even with the constraint that x does not equal 0. Unless I know why he thinks the LHS = 0 I do not know what to say.

In mathematics, you don't understand things. You just get used to them.
If it ain't broke, fix it until it is.
Always satisfy the Prime Directive of getting the right answer above all else.

Offline

## #25 2017-01-25 13:34:52

Hannibal lecter
Member
Registered: 2016-02-11
Posts: 225
Website

### Re: HI please solve this absolute value equation with interval notation ..

thank you ...

Wisdom is a tree which grows in the heart and fruits on the tongue

Offline