What is the solution to this question  or equation.   I=NE/(NR+E)
Solve for N. Assuming the numbers have no numerical value How can I
isolate N by it self so N=answer?

Hi smartstuff1282-ga,

Here are the steps required to solve this equation:

I=NE/(NR+E)

1. Move the RHS denominator to the left:
I*(NR+E) = NE

2. Distribute I:
INR+IE = NE

3. Collect all the terms with N in them:
IE = NE - INR

4. Factor out N
N*(E - IR) = IE

5. Divide through by (E-IR) to solve for N
N = IE/(E-IR)

So the final answer is:

N = IE /(E-IR)

Hopefully that helps.

Cheers!

answerguru-ga

An alternate route for this problem can be:

I = NE/NR+E

1/I = NR/NE + E/NE

1/I = R/E + 1/N

I = E/R + N

I - E/R = N

It's always nice to see an alternative approach. However, I believe
that the step in going from

1/I= R/E + 1/N

to

I = E/R + N

is in error.

It can be easier to see this with an example, e.g., let I=2, R=3, E=4, and N=-4.

1/I= R/E + 1/N
becomes
1/2 = 3/4 + 1/(-4)  (which is  true)

but
I = E/R + N
becomes
2=4/3 + (-4) (which is not true).

I think that this step needs to be restated for the alternative approach to work.

"However, I believe that the step in going from..."

   Yes, I see that you're correct about that.

qed100,

Thanks for not being defensive.

"To err is human" - and I can't begin to tell you how many mistakes I've made.

From another perspective, you should know that I've learned much from
your comments - I'm impressed by your knowledge.

> An alternate route for this problem can be:
> I = NE/NR+E
> 1/I = NR/NE + E/NE
> 1/I = R/E + 1/N
> I = E/R + N
> I - E/R = N

In addition to the mistake pointed out by brix24-ga, it's important to
note that you can *never* divide by a variable without considering
whether it's equal to zero.  Your first step assumes that I and NE are
both nonzero, which may not be true.

The Answerer did divide by E-IR, but notice that if E-IR = 0 (-> E =
IR), the problem has no solution anyway:

I = NE/(NR+E)
I = NIR/(NR+IR) = NIR/R(N+I) = NI/(N+I)
I(N+I) = NI
NI + I^2 = NI

It's impossible to isolate N in this system of equations, so it
doesn't really matter if you assume E = IR: you're only looking for
what N equals where it's defined.

First, it you have to ask, don't go into math.
Second, first answer is right.
Third, if E =IR there is no solution.
Forth, see the brackets in the original equations......

>Subject: Re: Math equation 
>From: frodo2366-ga on 27 Sep 2006 21:29 PDT     
>First, it you have to ask, don't go into math.

That's a fairly harsh comment to make. Irrelevant too, seeing as the
asker never made any comment regarding going into math in the first
place.

>Second, first answer is right.
>Third, if E =IR there is no solution.

Not strictly true. If E and I are both zero and R non-zero, there are
an infinite number of solutions for N.

>Forth, see the brackets in the original equations......