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General Forums => General Discussion => Topic started by: trust on November 16, 2005, 09:31:18 PM

Title: For You Math Wiz-Kids
Post by: trust on November 16, 2005, 09:31:18 PM
Help a brotha out.

Long Division:

5X^3 - 3X^2 - 4
---------------------
          X^2


Solve:

5x-4    = 2/3
5x+4                     

1                3                4
___     +    __        =    __
x-2            x+6          (x+3)(x-2)


Simplify:

1) (9x+81)/(x^2-9) * (2x^2-6x)/(x^2+18x+81)

2) (2/x^2-7x) + (3/x-7) - (3/x)

3) (1/x) + (1/y)
---------------------
(2/x) - (2/y)


Thanks.
Title: Re: For You Math Wiz-Kids
Post by: Sidoh on November 16, 2005, 09:33:30 PM
Get MathType.  My head hurts from reading that, damnit.

Haha, just kidding.  You seriously should check out MathType, though.  It's pretty neat.

Actually, I think Microsoft Word comes equipped with an "Equasion Editor," which is basically a light version of MathType.
Title: Re: For You Math Wiz-Kids
Post by: iago on November 16, 2005, 10:05:20 PM
What exactly are you doing to those equations?  I can change them into different equations, if that's what you want...

Quote from: OG Trust on November 16, 2005, 09:31:18 PM
5X^3 - 3X^2 - 4
---------------------
          X^2
5x - 3 - 4/x2

After that, it gets too long and boring.  I have better things to do :)
Title: Re: For You Math Wiz-Kids
Post by: MyndFyre on November 16, 2005, 11:20:45 PM
Quote from: OG Trust on November 16, 2005, 09:31:18 PM
Long Division:

5X^3 - 3X^2 - 4
---------------------
          X^2
Commutative property: you can split this into two fractions:
5x3 - 3x2       4
----------  -  -----
    x2               x2

Factor out x2, leaving you with :
5x - 3 - 4/x2

That's the most-simplified as that can get, and arguably the first form is even better.

Quote from: OG Trust on November 16, 2005, 09:31:18 PM
Solve:

5x-4    = 2/3
Multiply both sides by 3:
15x - 12 = 2
Add 12 to both sides
15x = 14
Divide both sides by 15
x = 14/15

Quote from: OG Trust on November 16, 2005, 09:31:18 PM
5x+4                     
1                3                4
___     +    __        =    __
x-2            x+6          (x+3)(x-2)
I don't know what you want out of those....  The second one, hrm.  Multiply both sides by (x+3)(x-2)
1(x+3) + [3(x2 - 5x - 6) / (x+6)] = 4
Make into common terms by multiplying 1(x+3) and 4 by (x+6)/(x+6)
[(x2 + 9x + 18)/(x+6)] + [3(x2 - 5x - 6)/(x+6)] = [(4x + 24)/(x+6)]
Multiply both sides by (x+6) to get a quadratic equation:
x2 + 9x + 18      +      3x2 - 5x - 6       =     4x + 24
Simplify
4x2 + 4x + 12 = 4x + 24
Divide both sides by 4:
x2 + x + 3 = x + 6
Subtract (x+6) from both sides:
x2 - 3 = 0

Solution: x2 = 3, so x = +/- sqrt(3)


Simplify:

Quote from: OG Trust on November 16, 2005, 09:31:18 PM
1) (9x+81)/(x^2-9) * (2x^2-6x)/(x^2+18x+81)
Separate each polynomial term into factors:
[9(x+9)] / [(x+3)(x-3)] * [2x(x-3)]/(x+9)2
Cross-cancel: one factor of (x+9), one factor of (x-3):
9/(x+3) * 2x/(x+9)
Multiply:
18x/[(x+3)(x+9)]
= 18x/(x2+12x+27)

Quote from: OG Trust on November 16, 2005, 09:31:18 PM
2) (2/x^2-7x) + (3/x-7) - (3/x)
2 / [x(x-7)] + 3/(x-7) - 3/x
Get everything in common terms: multiply the 2nd term by x/x and the third term by (x-7)/(x-7)
2/[x(x-7)] + 3x/[x(x-7)] - (3x-21)/[x(x-7)]
Combine like terms:
-19 / [x(x-7)], or -19/(x2 - 7x)

Quote from: OG Trust on November 16, 2005, 09:31:18 PM
3) (1/x) + (1/y)
---------------------
(2/x) - (2/y)
Separate them out.
[(1/x) / [(2/x)-(2/y)]]    +   [(1/y) / [(2/x)-(2/y)]]
Realize that 1/x means you can multiply the denominator by x
1 / (x[(2/x)-(2/y)])     +     1 / (y[(2/x)-(2/y)])
Distribute:
(1 / [2 - 2x/y]) + (1 / [2y/x - 2])
Whether that's actually more simple is anyone's argument :P
Title: Re: For You Math Wiz-Kids
Post by: d&q on November 16, 2005, 11:29:13 PM
 :-\ Reminds me of last year's math homework...
Title: Re: For You Math Wiz-Kids
Post by: Sidoh on November 16, 2005, 11:39:36 PM
Quote from: Deuce on November 16, 2005, 11:29:13 PM
:-\ Reminds me of last year's math homework...

Haha, reminds me of Geometry. :)
Title: Re: For You Math Wiz-Kids
Post by: Towelie on November 16, 2005, 11:53:24 PM
Quote from: Deuce on November 16, 2005, 11:29:13 PM
:-\ Reminds me of last year's math homework...
me too, what math are you in?
Title: Re: For You Math Wiz-Kids
Post by: trust on November 17, 2005, 05:50:31 AM
Thanks MyndFyre!

It's for analysis.

Title: Re: For You Math Wiz-Kids
Post by: trust on November 17, 2005, 05:48:24 PM
Mynd would you mind checking that again? I think you got some of the problems mixed up (like you took the denominator from one and put it with another... on a few?)
Title: Re: For You Math Wiz-Kids
Post by: MyndFyre on November 17, 2005, 08:10:15 PM
OK here's me checking it over, this time not trying to do it with ASCII fractions.  I started out with what I understood from your problems and worked step-by-step similarly (or identically) to the way I did it before:

1.) (http://www.jinxbot.net/pub/trust1a.gif)

2.) (http://www.jinxbot.net/pub/trust2a.gif)

3.) (http://www.jinxbot.net/pub/trust3a.gif)

Simplification problems:

1.) (http://www.jinxbot.net/pub/trust1b.gif)

2.) (http://www.jinxbot.net/pub/trust2b.gif)

3.) (http://www.jinxbot.net/pub/trust3b.gif)