Continue to Site

Welcome to EDAboard.com

Welcome to our site! EDAboard.com is an international Electronics Discussion Forum focused on EDA software, circuits, schematics, books, theory, papers, asic, pld, 8051, DSP, Network, RF, Analog Design, PCB, Service Manuals... and a whole lot more! To participate you need to register. Registration is free. Click here to register now.

solve equations help.

Status
Not open for further replies.

xhmv

Newbie level 3
Newbie level 3
Joined
May 22, 2008
Messages
4
Helped
0
Reputation
0
Reaction score
0
Trophy points
1,281
Location
California
Activity points
1,301
Hi folks,

I have 3 equations

xyz=a
x+y+z=b
xy+xz+yz=c

how could I find out x, y, z in terms of a, b and c? I don't have Matlab symbolic math at hands.

Merci.

Could anyone help me and tell me the results?
 

Hi,

your non-linear system can be solved quite easily by pen and paper.

multiply the second equation by x:

x^2 + x*y + x*z=b*x

but from the last one:

x*y+x*z = c - y*z

then:

x^2 + c - y*z = b*x

now, from the first equation:

y*z = a/x

then

x^2 + c - a/x = b*x

or, multiplying by x and rearranging:

x^3 - b*x^2 + c*x - a = 0 (for x <> 0)

solve it using the algorithm for the third degrees equation. Since the system is fully symmetrical, the three solution (if they exist) of the equation will be x, y and z
 

find the roots of x^3-bx^2+cx-a=0
Plot the above equation using any plotting tool, it will intersect the x axis at the values of x,y,z
 

use Maxima!!!!
It is very easy to use~
 

Status
Not open for further replies.

Part and Inventory Search

Welcome to EDABoard.com

Sponsor

Back
Top