# Solving equations simultaneously circuits

I really struggle with these and would just like someones input on how to best solve these, I can never seem to cancel everything out except the variable I am looking for. I have:

E-i1-Ri2=0
Ri2-Ri3=0
i1+i2+i3

I am looking to solve for i1

All R's are equal to 0.73 x10^6 ohms so I just simplified them all to R instead of R1 R2 and R3

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vela
Staff Emeritus
Homework Helper
Your first equation seems to be wrong because the units don't work out. I'll assume there's supposed to be an R before i1.

I'd start by rewriting them slightly so it's easier to see what to do:

Code:
R i1 + R i2        = E
R i2 - R i3 = 0
i1 +   i2 +   i3 = 0
Divide the first and second equations by R so all you have are currents on the left.

Code:
i1 + i2      = E/R
i2 - i3 = 0
i1 + i2 + i3 = 0
Can you see how you can get rid of i3 and end up with two equations involving just i1 and i2?

tiny-tim
Homework Helper
hi spottedcow913! (try using the X2 icon just above the Reply box )

just solve the equations one at a time

in this case, start with the middle one, and you get I2 = I3

now substitue that into the third one …

what do you get? 