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Thread: simultaneous equations, 3 unknowns

  1. #1
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    simultaneous equations, 3 unknowns

    Hey, need some help with the methodology involved in solving simultaneous equations with three unknowns.

    I1 = I2 + I3
    8I1= 3I3
    3I1+5I2=3.4

    cheers.
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  2. #2
    Super Member craig's Avatar
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    Quote Originally Posted by clayson View Post
    Hey, need some help with the methodology involved in solving simultaneous equations with three unknowns.

    I1 = I2 + I3
    8I1= 3I3
    3I1+5I2=3.4

    cheers.
    First rearrange your second two equations to get them with respect to $\displaystyle I1$

    $\displaystyle 8I1 = 3I3$, therefore $\displaystyle I3 = \frac{8}{3}I1$

    For the second one, do the same:

    $\displaystyle 3I1 + 5I2 = 3.4$, $\displaystyle 5I2 = 3.4 - 3I1$, so $\displaystyle I2 = \frac{3.4 - 3I1}{5}$.

    Now put these values of $\displaystyle I2$ and $\displaystyle I3$ in to your first equation, you now have an equation in terms of just $\displaystyle I1$.

    Solve this and then put your value for $\displaystyle I1$ back into the second and third equations to find all terms.
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