# Any math-smart people?

### #1

Posted 27 September 2008 - 01:00 AM

I can get so far, and then I just don't get it. Any explanations here would be hot.

The problem is "Find a polynominal function with the following zeros: 4, 3+ the square root of 7, 3- the square root of 7."

I can get it to the point that the equation reads "(x-4)(x squared-6x+2)". They give the answer as "x cubed -10x squared +26x-8". I just don't get how they do that. Can anyone help?

Sorry about typing out words, but I don't know how to type symbols. I'm getting desperate. Thanks.

### #2

Posted 27 September 2008 - 01:50 AM

Sure.

In a problem like that, you have to multiply each of the individual terms sort of like a traditional multiplication problem. If you have

123

__x45__

You would multiply every number in the top row by 5 and then by 4. It's not a perfect analogy, but I hope it helps.

In your problem, you will multiply the "x" from the first set of parentheses by each term in the second set of parentheses- x^2, -6x and 2. Then you multiply "-4" in the first set of parentheses by each term in the second set of parentheses as well. But your just expanding it into one long equation, so you get

x^3 - 6x^2 + 2x - 4x^2 + 24x - 8 =

**x^3 -10x^2 +26x - 8**

|____________||____________|

multiplying by x & multiplying by -4

Make sense? It's tough to type out on a forum like this.

### #3

Posted 27 September 2008 - 02:00 AM

Yes, when you put it out like that, it does make sense.

Thank you so very much.

Carry on, everyone, I've got homework to do!

### #4

Posted 27 September 2008 - 08:23 AM

Hi! (That's as far as I got in this thread.)

### #5

Posted 27 September 2008 - 05:16 PM

me too. im a total math retard.

my heart belongs to a canadian!

### #6

Posted 27 September 2008 - 05:53 PM

Polynomials are what made me withdraw from my algebra class.

Hope you're doing well with it, 55fan.

### #7

Posted 27 September 2008 - 06:32 PM

### #8

Posted 27 September 2008 - 07:01 PM

I can't do those problems. I start trying to figure out which route they're each taking. If one leaves Chicago and the other leaves LA, I figure if they aren't going to crash, they must be on different lines, but if one is taking the BNSF the whole way, and the other is taking the SP and the Rock Island (meeting in Tucamcari), then they won't crash, but they'll be travelling a different number of miles, so where they meet can be kind of tricky. If one takes a northern route through the Rockies, then they won't meet at all, but the TOA will be different.

Of course the books don't give you all of this information and still expect you to solve it. Evil people.

### #9

Posted 27 September 2008 - 07:35 PM

lol I got as far as "the problem is..." and then I couldn't read anymore.

when it comes to math I'm as stunned as a turnip

I'm more the history/political science/languages (especially Russian) type of geek.

### #10

Posted 27 September 2008 - 10:26 PM

### #11

Posted 28 September 2008 - 02:34 AM

I can get so far, and then I just don't get it. Any explanations here would be hot.

The problem is "Find a polynominal function with the following zeros: 4, 3+ the square root of 7, 3- the square root of 7."

I can get it to the point that the equation reads "(x-4)(x squared-6x+2)". They give the answer as "x cubed -10x squared +26x-8". I just don't get how they do that. Can anyone help?

Sorry about typing out words, but I don't know how to type symbols. I'm getting desperate. Thanks.

I teach math. Here's another way to look at it and I hope it shows up okay here:

(x-4)(x

^{2}-6x+2) is multiplying two terms. It's like finding the area of a rectangle. A = length times width

let the length be x-4 and the width be x

^{2}-6x+2

and set it up like this:

x

-4

x^{2}.....-6x.....+2

Now just multiply the parts.

x(x

^{2}) = x

^{3}

x(-6x) = -6x

^{2}

x(2) = 2x

-4(x

^{2}) = -4x

^{2}

-4(-6x) = 24x

-4(2) = -8

x........

**x**....

^{3}**-6x**....

^{2}**2x**

-4....

**-4x**....

^{2}**24x**....

**-8**

x^{2}.....-6x.....+2

Then just add up the parts:

x

^{3}- 6x

^{2}+ 2x - 4x

^{2}+ 24x - 8

and combine like terms

x

^{3}- 10x

^{2}+ 26x - 8

Hope that helps!

**Thank You, Steve Yzerman**!

### #12

Posted 28 September 2008 - 04:37 AM

That is a good way of doing it. Less confusion about if I had already done a particular combination.

You must be very smart if you teach.

### #13

Posted 28 September 2008 - 07:09 AM

Because hopefully they are on different train tracks.

### #14

Posted 28 September 2008 - 07:34 AM

Me too!

Math + me = Failure

*Captain Z!*

### #15

Posted 28 September 2008 - 09:17 AM

(x-4)(x

^{2}-6x+2) is multiplying two terms. It's like finding the area of a rectangle. A = length times width

let the length be x-4 and the width be x

^{2}-6x+2

and set it up like this:

x

-4

x^{2}.....-6x.....+2

Now just multiply the parts.

x(x

^{2}) = x

^{3}

x(-6x) = -6x

^{2}

x(2) = 2x

-4(x

^{2}) = -4x

^{2}

-4(-6x) = 24x

-4(2) = -8

x........

**x**....

^{3}**-6x**....

^{2}**2x**

-4....

**-4x**....

^{2}**24x**....

**-8**

x^{2}.....-6x.....+2

Then just add up the parts:

x

^{3}- 6x

^{2}+ 2x - 4x

^{2}+ 24x - 8

and combine like terms

x

^{3}- 10x

^{2}+ 26x - 8

Hope that helps!

NERD!

### #16

Posted 28 September 2008 - 12:43 PM

### #17

Posted 28 September 2008 - 03:39 PM

Of course the books don't give you all of this information and still expect you to solve it. Evil people.

My cousin works the railroad. I asked him about that, and he said that computers take care of the whole thing now.

I do like your analysis, though.

### #18

Posted 28 September 2008 - 07:23 PM

I can get so far, and then I just don't get it. Any explanations here would be hot.

The problem is "Find a polynominal function with the following zeros: 4, 3+ the square root of 7, 3- the square root of 7."

I can get it to the point that the equation reads "(x-4)(x squared-6x+2)". They give the answer as "x cubed -10x squared +26x-8". I just don't get how they do that. Can anyone help?

Sorry about typing out words, but I don't know how to type symbols. I'm getting desperate. Thanks.

If you need trigonometry, drop me a line. I could teach trig to a tree stump, teaching it to a person would be easy.

Ceterum autem censeo, Hudler esse delendam.

### #19

Posted 28 September 2008 - 08:47 PM

### #20

Posted 28 September 2008 - 11:31 PM

Thank you for the offer, but this algebra is the last class I need to graduate. Besides, I'm 1 1/2 times taller than a tree stump, twice as round, and 4 times the weight, which makes my density greater. I don't know by how much. That would involve geometry.

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