# Help: simple equation

Discussion in 'Math' started by gotumal, Jul 1, 2009.

1. ### gotumal Thread Starter Active Member

Mar 24, 2008
99
0

Here is a simple problem,

(i2+i3)-(i1+i4) X
------------- = ---
i1+i2+i3+i4 5

And

(i2+i4)-(i1+i3) Y
------------- = ---
i1+i2+i3+i4 5

Also,

i1+i2+i3+i4 = E

Can I find out i1, i2, i3 and i4 if I know X, Y and E?
What is the relation?

I tried with excel but could not do!

2. ### Ratch New Member

Mar 20, 2007
1,068
3
gotumal,

What does --- mean?
Are X,Y, and E constants?
What does i1+i2+i3+i4 5 mean?

It looks like you have 3 equations for at least 4 unknowns.
What does that tell you?

Ratch

Aug 15, 2007
536
26
<deleted>

--Rich

4. ### gotumal Thread Starter Active Member

Mar 24, 2008
99
0
The equations were,

[(i2+i3)-(i1+i4)]/[i1+i2+i3+i4]= X/5

And

[(i2+i4)-(i1+i3)]/[i1+i2+i3+i4] = Y/5

Also,

i1+i2+i3+i4 = E

I want to find out i1, i2, i3 and i4 with the values X, Y and E.

Actually there is a sensor which gives you the co-ordinates (X and Y) of a light spot faliing on it. And i1, i2, i3 and i4 are the four outputs. I was checking if it can be done reversed for my calculations.

Apart from above relation, there is more info like,

1. When (X,Y)=(0,0); i1=i2=i3=i4=E/4
2. When (X,Y)=(5,5),i2=E
2. When (X,Y)=(-5,5),i4=E
2. When (X,Y)=(5,-5),i3=E
2. When (X,Y)=(-5,-5),i1=E

Can we have another equation since we have four variables?

X and Y co-ordinates range which I am interested is -5 to +5.

5. ### someonesdad Senior Member

Jul 7, 2009
1,585
141
You've got three equations in four unknowns. There will be a continuum of solutions.

6. ### gotumal Thread Starter Active Member

Mar 24, 2008
99
0
Thanks someonesdad. OK, let me put it in other way,

I have a equation N/D = X/5

X range -5000 to +5000
N range -D to D (so the ranage of N/D -1 to +1)
D range 1000 to 10000

Now if I want to calculate X in the given range with step size of 1.5 i.e. total no. of results would be 10000/1.5 and not the coninous one,

Then what should be the mimimum step size of N and D