Math Is Fun Forum

bobbym

bumpkin

From: Bumpkinland

Registered: 2009-04-12

Posts: 109,606

Re: Last Assessment Please Help Me!!

Hi Bob;

Everytime I try to get further I lose some solutions or change the solution set. In addition I cannnot understand the OP's work. Can you help? I have to get off now.

---

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.

Bob

Administrator

Registered: 2010-06-20

Posts: 10,649

Re: Last Assessment Please Help Me!!

hi

I am honoured to do so, Jedi Master.

From

We want to divide by x, so consider the three cases:

now the first case is that x is more than 0
we can divide by x whilst leaving the sign the same

x<-3/2 but this is not compatible with x > 0 so no solutions here

the second case is x<0
we divide by x making the sign change

so -3/2<x<0

the third case is x=0 but then we get 0<0 which is always false

This looks good to me.  LATER EDIT ... BUT IT ISN'T ... READ ON!

But ..... why not get rid of the log at the start:

and so on .......

Bob

Last edited by Bob (2011-05-24 21:49:16)

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Children are not defined by school ...........The Fonz
You cannot teach a man anything;  you can only help him find it within himself..........Galileo Galilei
Sometimes I deliberately make mistakes, just to test you!  …………….Bob

bobbym

bumpkin

From: Bumpkinland

Registered: 2009-04-12

Posts: 109,606

Re: Last Assessment Please Help Me!!

Hi Bob;

I am honoured to do so, Jedi Master.

I prefer yogurt master, I think I will have a couple right now.

If I am wrong here I am going to look like the wrong end of a horse. I rejected -3/2<x<0 because when I plug x = - 5 / 4 into

I get .2328015... which is not greater than one.

Maple thinks the solution is:

Personally I hope the big M is wrong. Cause then I get to submit a bug report and am entitled to a years supply of banana-strawberry yogurt.

---

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.

gAr

Member

Registered: 2011-01-09

Posts: 3,482

Re: Last Assessment Please Help Me!!

Hi,

---

"Believe nothing, no matter where you read it, or who said it, no matter if I have said it, unless it agrees with your own reason and your own common sense"  - Buddha?

"Data! Data! Data!" he cried impatiently. "I can't make bricks without clay."

Bob

Administrator

Registered: 2010-06-20

Posts: 10,649

Re: Last Assessment Please Help Me!!

hi bobbym and gAr

Oh dear.  Ignored rule one:  try the numbers.

See below a table of values.  Looks like Maple is right and you're not the back end of a horse.

But why?  Seems to have an asymptote at approx x = -1

Working on it.

Arhhh!  log base 1.  That's a nasty twist.

So it would seem before you start this problem you have to:-

(i) eliminate in-admissable values in the square root ( ie x < -1.6 )

(ii) Then consider when the log is undefined ... cannot have log base 1 => undefined for x = -1

(iii) Decide how the fractional log base effects the evaluation when x < -1

Bob

Last edited by Bob (2011-05-24 21:54:16)

---

Children are not defined by school ...........The Fonz
You cannot teach a man anything;  you can only help him find it within himself..........Galileo Galilei
Sometimes I deliberately make mistakes, just to test you!  …………….Bob

anonimnystefy

Real Member

From: Harlan's World

Registered: 2011-05-23

Posts: 16,049

Re: Last Assessment Please Help Me!!

hi,

i found the solution and it says that x shuld be in the interval (-8/5,-3/2)u(-1,0)
didn't get how they came to that solution.

so -8/5<x<-3/2 or -1<x<0

Last edited by anonimnystefy (2011-05-24 22:08:07)

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“Here lies the reader who will never open this book. He is forever dead.
“Taking a new step, uttering a new word, is what people fear most.” ― Fyodor Dostoyevsky, Crime and Punishment
The knowledge of some things as a function of age is a delta function.

Bob

Administrator

Registered: 2010-06-20

Posts: 10,649

Re: Last Assessment Please Help Me!!

hi anonimnystefy

Yes that's what bobbym got in post #28.

In my post # 27 I agreed with your answer but I had missed out something.

Look at post # 30, where I have corrected that error and given the steps you need to go through, for this problem.

It's not an easy one at all.  It's had three of us trying to get there and using mathematical software to crunch out a solution.

But, post #30 shows you can get there without that, if you are careful.

An instructive question all round, I think. 

Post back if you want more detail on any step.

Also have a look at

http://www.mathisfunforum.com/viewtopic.php?id=4397

This will teach you how to make your maths look clearer on screen.

Bob

Last edited by Bob (2011-05-24 23:32:00)

---

Children are not defined by school ...........The Fonz
You cannot teach a man anything;  you can only help him find it within himself..........Galileo Galilei
Sometimes I deliberately make mistakes, just to test you!  …………….Bob

anonimnystefy

Real Member

From: Harlan's World

Registered: 2011-05-23

Posts: 16,049

Re: Last Assessment Please Help Me!!

hi bob bundy

so my problem would be:

i kinda had to edit it a million times to get it right.
hope i get the hang of it

Last edited by anonimnystefy (2011-05-24 23:44:46)

---

“Here lies the reader who will never open this book. He is forever dead.
“Taking a new step, uttering a new word, is what people fear most.” ― Fyodor Dostoyevsky, Crime and Punishment
The knowledge of some things as a function of age is a delta function.

Bob

Administrator

Registered: 2010-06-20

Posts: 10,649

Re: Last Assessment Please Help Me!!

hi

Wow, in the time it took to explain the corrections, I see you've made them and included the fraction.  Excellent!! 

So the rest of this post is pretty redundant.  That's great!

What! Only a million.  I need three million.

If you click on the Latex you'll see the code for it.  That way you can learn from other people's posts.  I do it all the time.

The curly brackets are used when you want the function to apply to more than one symbol that follows eg. the square root sign.

You can make the 5x/2 into a proper fraction but you've probably got enough to manage at the moment with that refinement.

Bob

Last edited by Bob (2011-05-24 23:48:25)

---

Children are not defined by school ...........The Fonz
You cannot teach a man anything;  you can only help him find it within himself..........Galileo Galilei
Sometimes I deliberately make mistakes, just to test you!  …………….Bob

anonimnystefy

Real Member

From: Harlan's World

Registered: 2011-05-23

Posts: 16,049

Re: Last Assessment Please Help Me!!

hi

isn't

the same as

---

“Here lies the reader who will never open this book. He is forever dead.
“Taking a new step, uttering a new word, is what people fear most.” ― Fyodor Dostoyevsky, Crime and Punishment
The knowledge of some things as a function of age is a delta function.

anonimnystefy

Real Member

From: Harlan's World

Registered: 2011-05-23

Posts: 16,049

Re: Last Assessment Please Help Me!!

if you don't have anything to do maybe you could help me a little bit with this. just so i can get the hang of it.

---

“Here lies the reader who will never open this book. He is forever dead.
“Taking a new step, uttering a new word, is what people fear most.” ― Fyodor Dostoyevsky, Crime and Punishment
The knowledge of some things as a function of age is a delta function.

Bob

Administrator

Registered: 2010-06-20

Posts: 10,649

Re: Last Assessment Please Help Me!!

hi

I think they are the same.

After all, neither means

do they?

What else do you want to make in Latex?

Bob

---

Children are not defined by school ...........The Fonz
You cannot teach a man anything;  you can only help him find it within himself..........Galileo Galilei
Sometimes I deliberately make mistakes, just to test you!  …………….Bob

anonimnystefy

Real Member

From: Harlan's World

Registered: 2011-05-23

Posts: 16,049

Re: Last Assessment Please Help Me!!

hi

I would like to know how to do matrices because i didn't understand anything about them in the topic you posted.
unrelated to this what limit rules apply for powers?

---

“Here lies the reader who will never open this book. He is forever dead.
“Taking a new step, uttering a new word, is what people fear most.” ― Fyodor Dostoyevsky, Crime and Punishment
The knowledge of some things as a function of age is a delta function.

gAr

Member

Registered: 2011-01-09

Posts: 3,482

Re: Last Assessment Please Help Me!!

Hi all,

A continuation of my explanation in case I wasn't clear enough...

Hi anonimnystefy,

You may like to try: http://www.codecogs.com/latex/eqneditor.php

Last edited by gAr (2011-05-25 00:28:40)

---

"Believe nothing, no matter where you read it, or who said it, no matter if I have said it, unless it agrees with your own reason and your own common sense"  - Buddha?

"Data! Data! Data!" he cried impatiently. "I can't make bricks without clay."

Bob

Administrator

Registered: 2010-06-20

Posts: 10,649

Re: Last Assessment Please Help Me!!

hi

Wow!  That's a huge topic with loads of applications and branches.

You'll need to learn how to multiply two matrices.

Have a look at

http://www.mathsisfun.com/algebra/matrix-multiplying.html

Then post again.

But I suggest you start a new thread with a matrix related title.

what limit rules apply for powers?

Don't understand the question.  Can you re-phrase it perhaps?

Bob

---

Children are not defined by school ...........The Fonz
You cannot teach a man anything;  you can only help him find it within himself..........Galileo Galilei
Sometimes I deliberately make mistakes, just to test you!  …………….Bob

bobbym

bumpkin

From: Bumpkinland

Registered: 2009-04-12

Posts: 109,606

Re: Last Assessment Please Help Me!!

Hi gAr, Bob;

Thanks for all the great work and ideas.

---

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.

anonimnystefy

Real Member

From: Harlan's World

Registered: 2011-05-23

Posts: 16,049

Re: Last Assessment Please Help Me!!

hi all

bob bundy, what i ment was is there anything you can do if you had something like this:

PS i did this one in 6 tries

Last edited by anonimnystefy (2011-05-25 07:23:49)

---

“Here lies the reader who will never open this book. He is forever dead.
“Taking a new step, uttering a new word, is what people fear most.” ― Fyodor Dostoyevsky, Crime and Punishment
The knowledge of some things as a function of age is a delta function.

bobbym

bumpkin

From: Bumpkinland

Registered: 2009-04-12

Posts: 109,606

Re: Last Assessment Please Help Me!!

Hi;

The x and the n are not related.

---

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.

anonimnystefy

Real Member

From: Harlan's World

Registered: 2011-05-23

Posts: 16,049

Re: Last Assessment Please Help Me!!

hi bobbym,

changed it,i'm just starting with this so i got confused

---

“Here lies the reader who will never open this book. He is forever dead.
“Taking a new step, uttering a new word, is what people fear most.” ― Fyodor Dostoyevsky, Crime and Punishment
The knowledge of some things as a function of age is a delta function.

anonimnystefy

Real Member

From: Harlan's World

Registered: 2011-05-23

Posts: 16,049

Re: Last Assessment Please Help Me!!

i forgot it should be

sorry

Last edited by anonimnystefy (2011-05-25 07:29:45)

---

“Here lies the reader who will never open this book. He is forever dead.
“Taking a new step, uttering a new word, is what people fear most.” ― Fyodor Dostoyevsky, Crime and Punishment
The knowledge of some things as a function of age is a delta function.

bobbym

bumpkin

From: Bumpkinland

Registered: 2009-04-12

Posts: 109,606

Re: Last Assessment Please Help Me!!

Hi;

That changes everything. Now you can just go ahead and take the limit of the numerator divided by the denominator.

---

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.

anonimnystefy

Real Member

From: Harlan's World

Registered: 2011-05-23

Posts: 16,049

Re: Last Assessment Please Help Me!!

hi bobbym

thought so but how?

---

“Here lies the reader who will never open this book. He is forever dead.
“Taking a new step, uttering a new word, is what people fear most.” ― Fyodor Dostoyevsky, Crime and Punishment
The knowledge of some things as a function of age is a delta function.

bobbym

bumpkin

From: Bumpkinland

Registered: 2009-04-12

Posts: 109,606

Re: Last Assessment Please Help Me!!

Hi;

From the limit rules.

---

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.

anonimnystefy

Real Member

From: Harlan's World

Registered: 2011-05-23

Posts: 16,049

Re: Last Assessment Please Help Me!!

hi

call me dumb but still not getting it

---

“Here lies the reader who will never open this book. He is forever dead.
“Taking a new step, uttering a new word, is what people fear most.” ― Fyodor Dostoyevsky, Crime and Punishment
The knowledge of some things as a function of age is a delta function.

bobbym

bumpkin

From: Bumpkinland

Registered: 2009-04-12

Posts: 109,606

Re: Last Assessment Please Help Me!!

Okay, do them one at a time now.

This one can be done by inspection. See the term 2010^(2010x)? As x goes to minus infinity the exponent is going to go to - infinity. Minus powers in the exponent mean 1 over. For instance

What you are going to get here is:

( ordinarily we do not write such things as 1 / ∞ = 0. Because ∞ is not a number. But what I mean here is as x approaches infinity 1 / x approaches 0. )

So

Give the denominator a try. Do not worry, I will help if you get stuck.

---

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.