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

You are not logged in.

- Topics: Active | Unanswered

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

x(x-1)(x+1)

do I multiply the brackets by eachother first, or each bracket by x?

Aloha Nui means Goodbye.

Offline

**ganesh****Moderator**- Registered: 2005-06-28
- Posts: 16,332

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.

Character is who you are when no one is looking.

Offline

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

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)*

Offline

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

Thankyou, I was drunk

Won't happen again.

Aloha Nui means Goodbye.

Offline

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

Maybe someone could simplify this?

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

Offline

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

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.

Offline

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

well the answer is

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

Offline

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

Sounds like a job for Crazy Holmes

Aloha Nui means Goodbye.

Offline

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

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.

Offline

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

yeah, maybe you're right.

Offline

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

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

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

### ### ### ###

# # # # # # #

# ## # # # # # #

# # # # # # # #

### ### ### ###

IPBLE: Increasing Performance By Lowering Expectations.

Offline

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

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.

Offline

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

appologise, grassy homes.

Aloha Nui means Goodbye.

Offline

**ganesh****Moderator**- Registered: 2005-06-28
- Posts: 16,332

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.

Character is who you are when no one is looking.

Offline

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

Yes, wildrocky, yes.

IPBLE: Increasing Performance By Lowering Expectations.

Offline

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

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.

Offline

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

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.

Offline

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

Yes, but the "a" cannot be removed.

IPBLE: Increasing Performance By Lowering Expectations.

Offline