Math problem > General Discussion

Posted: 10/16/2007 7:30:20 PM EDT

I should know this but I'm just not sure of my answer..

The original question is:

((x^2-3x-18)/(x^2+5x+6))*((x^3-64)/(x^2-16))

I factor it down to this and get stuck..

(((x-6)(x+3))/((x+2)(x+3)))*(((x-4)(x^2+4x+16))/((x+4)(x-4)))

Then cancel out to get

(((x-6)~~(x+3)~~)/((x+2)~~(x+3)~~))*((~~(x-4)~~(x^2+4x+16))/((x+4)~~(x-4)~~))

And then get stuck, cause Towely's an idiot..

Or is that as far as you can go?

Posted: 10/16/2007 7:44:31 PM EDT

[#1]

You factored wrong. x^3 - 64 = (x-4) * (x^2 + 4x + 16). That doesn't factor though, so I think you're still stuck.

Posted: 10/16/2007 7:45:24 PM EDT

[#2]

Fuck I have no idea, I'm a history major for a reason...

Good luck to you though.

Posted: 10/16/2007 7:46:45 PM EDT

[#3]

Quoted:
You factored wrong. x^3 - 64 = (x-4) * (x^2 + 4x + 16). That doesn't factor though, so I think you're still stuck.

Oops, that's how I did it. I typed it in wrong..

Either way im stuck. Maybe thats the answer..

Posted: 10/16/2007 7:50:29 PM EDT

[#4]

Quoted:

Quoted:
You factored wrong. x^3 - 64 = (x-4) * (x^2 + 4x + 16). That doesn't factor though, so I think you're still stuck.

Oops, that's how I did it. I typed it in wrong..

Either way im stuck. Maybe thats the answer..

yeah, you cant factor that down anymore

Posted: 10/16/2007 7:50:38 PM EDT

[#5]

I get two answers, depending on whether you're learning about polynomial long division and remainders...

Posted: 10/16/2007 7:55:10 PM EDT

[#6]

(x-6)(x+4) / (x+2)(x^2+4x+16)

Posted: 10/16/2007 7:58:36 PM EDT

[#7]

Quoted:
(x-6)(x+4) / (x+2)(x^2+4x+16)

Close, but it should be (x-6)(x^2+4x+16) / (x+2)(x+4)

Posted: 10/16/2007 8:01:03 PM EDT

[#8]

87

Posted: 10/16/2007 8:03:08 PM EDT

[#9]

Quoted:
87

That is what I came up with also

Posted: 10/16/2007 8:03:52 PM EDT

[#10]

Quoted:

Quoted:
(x-6)(x+4) / (x+2)(x^2+4x+16)

Close, but it should be (x-6)(x^2+4x+16) / (x+2)(x+4)

You sure?

I get (x-6) / (x+2) divided by (x+4) / (x^2+4x+16)

Then you invert before you multiply which gives you the

(x-6)(x+4) / (x+2)(x^2+4x+16)

By edging them together you are intending to multiply them and the original equation said they were to be factored then divided.

ETA: Oh shit, I thought they were to be divided after being factored so I inverted the second equation.

Ma bad.

Posted: 10/16/2007 8:06:23 PM EDT

[#11]

Quoted:

Quoted:
(x-6)(x+4) / (x+2)(x^2+4x+16)

Close, but it should be (x-6)(x^2+4x+16) / (x+2)(x+4)

+1

Posted: 10/16/2007 8:12:13 PM EDT

[#12]

I don't see a question. I don't even see an equal sign. what is the problem? are you supposed to simplify?

Posted: 10/16/2007 8:14:17 PM EDT

[#13]

Quoted:
I don't see a question. I don't even see an equal sign. what is the problem? are you supposed to simplify?

Actually, Factor, simplify, then multiply.

Posted: 10/16/2007 8:16:10 PM EDT

[#14]

Quoted:

Quoted:
(x-6)(x+4) / (x+2)(x^2+4x+16)

Close, but it should be (x-6)(x^2+4x+16) / (x+2)(x+4)

You sure?

I get (x-6) / (x+2) divided by (x+4) / (x^2+4x+16)

Then you invert before you multiply which gives you the

(x-6)(x+4) / (x+2)(x^2+4x+16)

By edging them together you are intending to multiply them and the original equation said they were to be factored then divided.

ETA: Oh shit, I thought they were to be divided after being factored so I inverted the second equation.

Ma bad.

Yes, you caught yourself. To multiply fractions, multiply the numerators and multiply the denominators. To go further, multiply the numerator and the denominator (separately) and then do polynomial long division (with a remainder).

Posted: 10/16/2007 8:17:31 PM EDT

[#15]

Another example of polynomial long division

Posted: 10/16/2007 8:17:56 PM EDT

[#16]

Quoted:

Quoted:
(x-6)(x+4) / (x+2)(x^2+4x+16)

Close, but it should be (x-6)(x^2+4x+16) / (x+2)(x+4)

You sure?

I get (x-6) / (x+2) divided by (x+4) / (x^2+4x+16)

Then you invert before you multiply which gives you the

(x-6)(x+4) / (x+2)(x^2+4x+16)

By edging them together you are intending to multiply them and the original equation said they were to be factored then divided.

ETA: Oh shit, I thought they were to be divided after being factored so I inverted the second equation.

Ma bad.

Yes, you caught yourself. To multiply fractions, multiply the numerators and multiply the denominators. To go further, multiply the numerator and the denominator (separately) and then do polynomial long division (with a remainder).

God I hated PLD.

Posted: 10/16/2007 8:33:11 PM EDT

[#17]

Quoted:

Quoted:
I don't see a question. I don't even see an equal sign. what is the problem? are you supposed to simplify?

Actually, Factor, simplify, then multiply.

I'd just substitute x=1 and simplify. answer is 7.

or:

(8-x) + (32x-32)/(x^2+6x+8)

eta for typo

Posted: 10/16/2007 8:52:01 PM EDT

[#18]

... (x^2+4x+16)(x-6)/(x+4)(x+2)

Posted: 10/16/2007 8:56:13 PM EDT

[#19]

FOIL

first, outer, inner, last

Posted: 10/16/2007 9:10:03 PM EDT

[#20]

Quoted:

Quoted:
87

That is what I came up with also

Same here.

Towely, what part of Wi are you in?

Posted: 10/16/2007 9:24:56 PM EDT

[#21]

Quoted:
FOIL

first, outer, inner, last

My teacher taught us this new way to do that that was really cool.

_______ x-5
_______ x+5
________ ------
________+5x-25
____x^2-5x
-----------------
____x^2____-25

Cross multiply just like regular multiplication.

I thought it was cool, pretty simple.

Ignore the __ just used for proper spacing.

Posted: 10/16/2007 9:52:09 PM EDT

[#22]

Quoted:

Quoted:
87

That is what I came up with also

Same here.

Towely, what part of Wi are you in?

SE. I'm about a 30 minute drive south of Milwaukee.

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