Math Is Fun Forum

jef111

Guest

3 unknowns

hi if anybody can help me on this equation id be grateful

I1 +I2 +I3 = 0
50I1 + 30I2 = 16
-20I2 + 5I3 = -6

many thanks

bobbym

bumpkin

From: Bumpkinland

Registered: 2009-04-12

Posts: 109,606

Re: 3 unknowns

Hi;

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In mathematics, you don't understand things. You just get used to them.
If it ain't broke, fix it until it is.
Always satisfy the Prime Directive of getting the right answer above all else.

jeff111

Guest

Re: 3 unknowns

hi thanks any chance of how you did it so i can understand it

bobbym

bumpkin

From: Bumpkinland

Registered: 2009-04-12

Posts: 109,606

Re: 3 unknowns

HI;

Multiply equation 1 by 5 and subtract equation 3 from it.

You get:

Now work with equation 2 and that to get:

Now times the second equation by 10 and Now subtract the first from it:

l2 = 1 / 5

Now we have one variable solved for go up to the original 3 equations and plug in to the second equation.

Plug in l2

l1 = 1 / 2.

Now take l1 and l2 and plug into the top equation.

l3 = - 2 / 5

---

In mathematics, you don't understand things. You just get used to them.
If it ain't broke, fix it until it is.
Always satisfy the Prime Directive of getting the right answer above all else.

jeff111

Guest

Re: 3 unknowns

thanks for that helped me out loads

bobbym

bumpkin

From: Bumpkinland

Registered: 2009-04-12

Posts: 109,606

Re: 3 unknowns

Hi jeff111;

You are welcome, check post #4 for the whole solution but give me a minute to check it.

---

In mathematics, you don't understand things. You just get used to them.
If it ain't broke, fix it until it is.
Always satisfy the Prime Directive of getting the right answer above all else.