Algebra help, Kirchoffs rule problem.

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SUMMARY

The discussion revolves around solving for the current I3 using Kirchhoff's rule in a circuit equation. The user initially misapplies algebraic manipulation, leading to confusion regarding the transition from the equation 4E/R - 9I3/2 = I3 to the correct form. The correct interpretation involves multiplying the entire equation by 2, resulting in 8E/2R - 9I3 = 2I3, clarifying the derivation of the term 2I3/2. Ultimately, the user resolves their misunderstanding regarding the algebraic steps involved in isolating I3.

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  • Understanding of Kirchhoff's laws in electrical circuits
  • Basic algebraic manipulation techniques
  • Familiarity with solving linear equations
  • Knowledge of current and voltage relationships in circuits
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Students studying electrical engineering, educators teaching circuit analysis, and anyone seeking to improve their algebra skills in the context of electrical circuits.

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Hey guys, I'm having a little trouble with some basic algebra. I'm working on solving for currents using kirchhoffs rule.

4E/R - 9I3/2 = I3

Trying to solve for I3... I should get:
8E/2R -9I3 = 2(I3).. and then 8E/2R = 11(I3).. and then I3= 4E/11R

However I am looking at my teachers solution and her answer was:

4E/R - 9I3/2 = I3
4E/R = 2I3/2 + 9I3/2 = 11I3/2 . How did she get the 2I3/2? It doesn't make sense to me. Once again, I am trying to solve for I3.

Please help, I really appreciate it. Thanks.
 
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Look at your first equation again. You did two things in that equation. There is your error.
 
I don't understand..

How did I do 2 things?
If I'm left with 8E/2R = 11(I3), then finding I3 would be dividing both sides by 11, which would not give me the correct answer.

Also, that doesn't explain where she got the 2I3/2 on the right side. Thats what I'm concerned about.

Still stuck, thanks for the help, but I don't quite understand it.
 
Last edited:
How did you go from - 9I3/2 to -9I3?
 
I multiplied both sides of the equation by 2.
 
Did you multiply each term by 2?
 
yes..

4E/R - 9I3/2 = I3

x 2

8E/2R - 9I3 = 2I3
 
Nevermind..
I"m stupid.. I figured it out.

Thanks man.
 
4*2=8. right?
 
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no problem friend
 

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