# HP Forums

Full Version: calculator solving linear eqns in terms of unknown
You're currently viewing a stripped down version of our content. View the full version with proper formatting.
My friends less expensive ti solves a 3x4 system of linear equations in terms of 4th unknown. How do i do this on my prime?

Example
2a+2b+2c=0
3a+b+2c=0
a+b+c=W

I want to get all my variables in terms of W. The type of problem im solving is a statics problem and im asked to find the maximum weight of flowerpot if the chain can hold a max 50lb tension. So W represents the maximum weight (flowerpot) that the system can hold. How do i input this?
(10-02-2016 05:26 PM)yland Wrote: [ -> ]2a+2b+2c=0
3a+b+2c=0
a+b+c=W
your 3rd and 1st equation says that W is useless in your system. (divide by 2 your first equationto see it)
lets change your 3rd equation by : a+b+2c=W

then you can use linsolve to get it :

linsolve([2*a+2*b+2*c=0 3*a+b+2*c=0 a+b+2*c=w],[a b c])
it gives : [-1/2*w, -1/2*w w]
that's a,b and c in term of w.
Thank you primer. Appreciate the help
Im getting error: bad argument value
(10-02-2016 08:51 PM)yland Wrote: [ -> ]Im getting error: bad argument value

Try:

linsolve([2*a+2*b+2*c=0,3*a+b+2*c=0,a+b+2*c=w],[a,b,c])

Mark Hardman
(10-02-2016 05:26 PM)yland Wrote: [ -> ]My friends less expensive ti solves a 3x4 system of linear equations in terms of 4th unknown. How do i do this on my prime?

Example
2a+2b+2c=0
3a+b+2c=0
a+b+c=W

I want to get all my variables in terms of W. The type of problem im solving is a statics problem and im asked to find the maximum weight of flowerpot if the chain can hold a max 50lb tension. So W represents the maximum weight (flowerpot) that the system can hold. How do i input this?

There is something about your system that does not sound right to me: 2*a+2*b+2*c=0 --> (a+b+c)=0 then W=0.
Could you please rewrite the exact equations ?
Best,

Aries ;-)
thanks for the replies and help, those are not actual eqns I just wanted to give an idea of the form I was dealing with. I figured out why I was getting the error, I was not aware of the different ways to access linsolve command. Basicly I was using LinSolve. Now all is well thanks again.
(10-03-2016 05:11 PM)yland Wrote: [ -> ]thanks for the replies and help, those are not actual eqns I just wanted to give an idea of the form I was dealing with. I figured out why I was getting the error, I was not aware of the different ways to access linsolve command. Basicly I was using LinSolve. Now all is well thanks again.

You're welcome, yland ;-)
Best,

Aries :-)
Reference URL's
• HP Forums: https://www.hpmuseum.org/forum/index.php
• :