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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- Dec 8th 2009, 04:57 AMclaysonsimultaneous equations, 3 unknowns
Hey, need some help with the methodology involved in solving simultaneous equations with three unknowns.

*I*1 =*I*2 +*I*3

8*I*1= 3*I*3

3*I*1+5*I*2=3.4

cheers. - Dec 8th 2009, 06:42 AMcraig
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.