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

RickyOswaldIOW
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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?


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

ganesh
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Registered: 2005-06-28
Posts: 13,590

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.


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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 smile

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 sad
Won't happen again.


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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?

grint1km.jpg
again, I need the whole solution, because the answer is at the end of the book wink

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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)


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

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

Re: Simplify

well the answer is boo8rp.jpg
I also tried to do that but in quite different way. Still I couldnt get the right answer. That's what I got
too3rf.jpg

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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 wink


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

krassi_holmz
Real Member
Registered: 2005-12-02
Posts: 1,908

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. sad

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

krassi_holmz
Real Member
Registered: 2005-12-02
Posts: 1,908

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: 1,908

Re: Simplify

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


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: 13,590

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. smile


Character is who you are when no one is looking.

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

krassi_holmz
Real Member
Registered: 2005-12-02
Posts: 1,908

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 **...


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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: 1,908

Re: Simplify

Yes, but the "a" cannot be removed.


IPBLE:  Increasing Performance By Lowering Expectations.

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