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November 27th, 2011, 07:25 PM   #1
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another weird problem... help

solve the system, answer with an ordered triple:
2x-5y+4z-3w=-7
x+6y+7z-w=-14
3x-2y+w=5
4x+y-8z=3

What the heck is this? I am at college algebra matrix section, but these numbers are impossibly complicated for this level of algebra.

So I put this in box matrix box and do rref=

2 -5 4 -3 -7
1 6 7 -1 -14
3 -2 0 1 5
4 1 -8 0 3


I get
1 0 0 0 -(55/379)
0 1 0 0 -(411/379)
0 0 1 0 -(211/379)
0 0 0 1 (1238/379)

so x = -(55/379), y= -(411/379), z= -(221/379), w= (1238/379).
When I use calculator and plug these #s in, I get right answer. but is this even right? Am I understanding question wrong or is this suppose to be some crazy problem that's supposed to get this kind of complicated # and can only be done by calculator? help..
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November 27th, 2011, 07:34 PM   #2
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Re: another weird problem... help

Those values agree with what I get too.

I suspect you are either to use calculator/computer or Gaussian elimination.
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November 27th, 2011, 08:23 PM   #3
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Re: another weird problem... help

thx. You are my lifesaver. Am I suppose to put answer in { (x,y,z,w) } format or something else?
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November 27th, 2011, 08:54 PM   #4
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Re: another weird problem... help

It says to answer with an ordered triple, but there are 4 variables, so I would use an ordered quadruple (w,x,y,z).
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November 29th, 2011, 11:45 AM   #5
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Quote:
Originally Posted by shin777
. . . these numbers are impossibly complicated . . .
Are you sure all the coefficients and signs in the given equations are correct?
For example, the equations
2x - 5y + 4z - 3w = -77
x + 6y + 7z - w = 34
3x - 2y + w = 5
4x + y - 8z = 3
are similar and the corresponding values of w, x, y and z are all integers.
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