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Hello my lovely community, I have this equation : 

 

0 = I1/r - I2/r+d

 

 By the way the 1 at I1 is an index. Same goes for I2.

 

I want to solve this equation for r but I am helpless :(

Could anyone help me and show it to me step by step ?

 Oct 19, 2017
 #1
avatar+98125 
+1

Is the equation

 

0   =  I^(1/r) - I^(2/r) +  d     ????

 

Or is it

 

0  =  I^1  / r  +  I^(2) / r  + d      ????

 

 

cool cool cool

 Oct 19, 2017
edited by CPhill  Oct 19, 2017
 #2
avatar+27 
0

The 1 at I1 and the 2 at I2 are just an index. In this exaple I1 is electricity number 1 and I2 is electricity number 2 :)!

Theoretical I could write : 0 = y/r - x/r+d 

and now I want to solve for r :3

Sekai  Oct 19, 2017
 #3
avatar+98125 
+2

Oh...OK....I understand now

 

We have that

 

0  =  I1 / r  + I2 / r  + d     subtract   d from both sides

 

-d  =   I1 / r  + I2 / r       note that the right side can be written as

 

-d =   [  I1 + I2 ]  / r      multiply both sides by r

 

-rd  =   I1 + I        divide both sides by -d

 

r =     [  I1 + I2 ]  /  -d 

 

r  =   - [ I1 + I2 ] / d  

 

 

cool cool cool

 Oct 19, 2017
 #4
avatar+27 
0

Thank you !

(I also learned to make an index. I<-- haha.)

Sekai  Oct 19, 2017
 #5
avatar+98125 
+2

 

 

P.S.  ......if the "d"  is supposed to be a part of the second denominator, we have

 

0  =  I1 / r  + I2 /  (r  + d)      get a common denominator

 

0 =   [ I1 ( r + d)  +  Ir ]  /  [ r (r + d) ]      multiply boh sides by   [ r (r + d) ]

 

0 *  [ r (r + d) ]  =   [ I1 ( r + d)  +  Ir ] 

 

0  =   [ I1 ( r + d)  +  I2 r ]    simplify

 

0  =  I1 r + I1d +   I2 r       subtract  I1d  from both sides

 

- I1d     =    I1 r  +   I2 r      factor the right side

 

- I1d   =   r  [ I1 + I2 ]         divide both sides by  [ I1 + I2

 

- I1d  /   [ I1 + I2 ]    =   r

 

 

cool cool cool

 Oct 19, 2017
 #8
avatar+27 
+1

Yessssss I was wondering the whole day about the equation since I've seen it before and it was more like the second one. 

I am sry for my mistake but thanks that you're so mindfully!

Sekai  Oct 20, 2017
 #6
avatar+98125 
+2

One last thing, Sekai

 

The  "1"    and  "2"   are known as "subscripts"

 

"Indexes"  usually refer to exponents

 

 

cool cool cool

 Oct 19, 2017
 #7
avatar+27 
+1

Well I am learning Math and Physik in german and my teacher alway say to Subscripts index so I was assuming it was the same in english haha :c 

But thanks. 

Learning by mistakes ! :D

Sekai  Oct 20, 2017

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