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## #1 2006-01-05 19:35:33

RickyOswaldIOW
Member
Registered: 2005-11-18
Posts: 212

### Simplify

x(x-1)(x+1)
do I multiply the brackets by eachother first, or each bracket by x?

Aloha Nui means Goodbye.

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## #2 2006-01-05 19:48:00

ganesh
Moderator
Registered: 2005-06-28
Posts: 21,812

### Re: Simplify

Multiplication is commutative, that is 6 x 7 = 7 x 6.
When you have three terms to be multiplied, first multiply the first and the second and the result by the third.It wouldn't make a difference if you multiply the second and the third and then multiply the result by the first.
x(x-1)(x+1) = (x²-x)(x+1) = x³ + x² - x² - x = x³ - x.
(x-1)(x+1)(x) = (x² - 1)(x) = x³ - x
As you can see, the results are the same in both the cases.

When you have a(x-y), you'd have to multiply both the terms inside the bracket by a, you get ax - ay.

It is no good to try to stop knowledge from going forward. Ignorance is never better than knowledge - Enrico Fermi.

Nothing is better than reading and gaining more and more knowledge - Stephen William Hawking.

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## #3 2006-01-05 21:53:46

Rose-Red
Member
Registered: 2006-01-05
Posts: 19

### Re: Simplify

or you simply can see a formula (a-b)(a+b)=a² - b² ; as a result (x-1)(x+1)=x²-1²
so x(x-1)(x+1)=x(x²-1²)=x³-x

Last edited by Rose-Red (2006-01-05 21:54:54)

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## #4 2006-01-06 09:36:37

RickyOswaldIOW
Member
Registered: 2005-11-18
Posts: 212

### Re: Simplify

Thankyou, I was drunk
Won't happen again.

Aloha Nui means Goodbye.

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## #5 2006-01-06 09:59:01

Rose-Red
Member
Registered: 2006-01-05
Posts: 19

### Re: Simplify

Maybe someone could simplify this?

again, I need the whole solution, because the answer is at the end of the book

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## #6 2006-01-06 10:06:12

RickyOswaldIOW
Member
Registered: 2005-11-18
Posts: 212

### Re: Simplify

I'd start with x/x^2, firstly I'd "reciprocal" which basically means you take the value with the power (x^2) and move it to the top, when you do this you MUST change the sign of the power:

x / x^2  = x * x^-2

I'd then do the same with the next part of the sum, giving you b - ax * x^-3.  Now all that is left is

(x * x^-2) + (b - ax * x^-3), since none of the values share similar powers, I think this is as far as you can go.  (Don't take my word for it, I'm new to this too).

Last edited by rickyoswaldiow (2006-01-06 10:06:35)

Aloha Nui means Goodbye.

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## #7 2006-01-06 10:23:02

Rose-Red
Member
Registered: 2006-01-05
Posts: 19

### Re: Simplify

I also tried to do that but in quite different way. Still I couldnt get the right answer. That's what I got

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## #8 2006-01-06 10:41:02

RickyOswaldIOW
Member
Registered: 2005-11-18
Posts: 212

### Re: Simplify

Sounds like a job for Crazy Holmes

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## #9 2006-01-06 10:53:31

krassi_holmz
Real Member
Registered: 2005-12-02
Posts: 1,905

### Re: Simplify

I think the book's answer isn't correct. We can't eliminate a.
I got the same as you.

IPBLE:  Increasing Performance By Lowering Expectations.

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## #10 2006-01-06 10:54:31

Rose-Red
Member
Registered: 2006-01-05
Posts: 19

### Re: Simplify

yeah, maybe you're right.

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## #11 2006-01-06 10:58:36

krassi_holmz
Real Member
Registered: 2005-12-02
Posts: 1,905

### Re: Simplify

I've just read this "crazy holmes" thing.

Ha, ha, ha, that was VERY VERY... VERY
###     ###    ###   ###
#          #    #  #    #  #    #
#   ##  #     # #     #  #    #
#    #   #     # #     #  #    #
###     ###    ###   ###

IPBLE:  Increasing Performance By Lowering Expectations.

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## #12 2006-01-06 11:01:22

krassi_holmz
Real Member
Registered: 2005-12-02
Posts: 1,905

### Re: Simplify

Actually it was BAD, but I'll forgive you if you promise that you will
NEVER
NEVER
NEVER
do this again
much

IPBLE:  Increasing Performance By Lowering Expectations.

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## #13 2006-01-06 11:19:11

RickyOswaldIOW
Member
Registered: 2005-11-18
Posts: 212

### Re: Simplify

appologise, grassy homes.

Aloha Nui means Goodbye.

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## #14 2006-01-06 16:39:50

ganesh
Moderator
Registered: 2005-06-28
Posts: 21,812

### Re: Simplify

Very funny. First krassi_holmz becomes crazy holmes, finally, grassy homes. I really hope krassi_holmz doesn't take offence at that. Maybe, rickyoswaldiow is just being funny. But a word of caution to rickyoswaldiow. People don't like their names (or usernames) spelt or pronouned wrongly.

It is no good to try to stop knowledge from going forward. Ignorance is never better than knowledge - Enrico Fermi.

Nothing is better than reading and gaining more and more knowledge - Stephen William Hawking.

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## #15 2006-01-06 22:35:27

krassi_holmz
Real Member
Registered: 2005-12-02
Posts: 1,905

### Re: Simplify

Yes, wildrocky, yes.

IPBLE:  Increasing Performance By Lowering Expectations.

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## #16 2006-01-07 04:31:12

RickyOswaldIOW
Member
Registered: 2005-11-18
Posts: 212

### Re: Simplify

No offence intended.  I play online FPS games and my language in that would get me banned in a flash here. You **...

Aloha Nui means Goodbye.

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## #17 2006-01-07 04:56:01

mathsyperson
Moderator
Registered: 2005-06-22
Posts: 4,900

### Re: Simplify

I'm a bit late here, but I agree with everyone else.

I'd just scale up the left fraction by x to get a common denominator of x³, and then they can easily be added together.

Why did the vector cross the road?
It wanted to be normal.

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## #18 2006-01-07 05:41:20

krassi_holmz
Real Member
Registered: 2005-12-02
Posts: 1,905

### Re: Simplify

Yes, but the "a" cannot be removed.

IPBLE:  Increasing Performance By Lowering Expectations.

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