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I'm pretty dumb for math Can somebody tell me if a equation system with three unknowns and three equations can be solved using the substitution or equalization (not sure if ...
  1. 02-01-2007 #1
    Juan Pablo
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    Simple math question

    I'm pretty dumb for math

    Can somebody tell me if a equation system with three unknowns and three equations can be solved using the substitution or equalization (not sure if this is the correct name in english) method?.

    Most books use the reduction method but I don't see why you can't use the substitution method

    This forum is full of intelligent people. I don't want you to do my homework but I would like just this answer.
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  2. 02-01-2007 #2
    benjamin20
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    never was good with the terminology, but is substitution where you salve one equasion for x, plug that equasion in for x in another problem solve it out for y, then plug that into last equasion along with the x equasion, replacing the interior y's, and then solve out for z, then plug z in for the first and second equasion, creating a simplified set of equasions where you now sove for the new x and y.

    i moght have it wrong, its been forever since ive had to use it.
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  3. 02-01-2007 #3
    Juan Pablo
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    You got it right!! Thanks!!
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  4. 02-01-2007 #4
    benjamin20
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    i did, im suprised, sounded too stupid to be it. whats the reduction method then
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  5. 02-01-2007 #5
    theamazingtwoeyedman
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    Whats the EQ?
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  6. 02-01-2007 #6
    apoorv_khurasia
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    You can solve the system of equations by any method provided they are consistent. (that can be checked by calculating the determinant of co-efficients, it must be non-zero for consistency). All these methods are just fancy names for the same thing (we call this equivalence in maths).

    Hope this helps you.
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  7. 02-02-2007 #7
    michaellouis
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    yes, you can solve using the substitution method but with three equations and three unknowns. But, it's going to get very messy and because of that reason it will be very easy to make a small mistake that will give you the wrong solution.

    Basically, the idea would be take on equation and solve for one variable. substitute that one variable into the other two equations. then you will be left with two equations and two unknowns. Now you can solve for the other two variables with those two resulting equations that are left. And you can use substitution again if you want.

    The main mistake that I see (I'm a math teacher) is people seem to try to substitute in an equation twice. If that makes any sense.

    But you are right it substitution will still work with three equations on principal.
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  8. 02-03-2007 #8
    Juan Pablo
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    Thanks michaellouis!

    Right now I'm trying to use the elimination or reduction method instead, it seems much simpler.

    BTW, I hate exams, I always can solve equation in homeworks but I can't in exams
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