# Problem with four system ode matlab

1. May 19, 2012

### a.gema

Hi,
I am a newbie to matlab
I have 4 equations ode to a system,

dxdt=-c*z*s')

dydt=((-1.021*(y^2))/(b+a))-(2.081015257+(6.936717523*x))/(b+a)+((p*r)-(p*j)/(b+a))-(((p^2)-2*p*(s^2)*c*z^2))/2*p')

dzdt=(((p^2)*r)-((p^2)*j))/(((S*x)+((p^2)*r))-((p^2)*j)/(b+a))-(((z^2)*c*(p^2))/(2*s*x))+(((z^2)*c*(s^2))/(2*s*x))-((z^2)*c*((p-s)^2)/2*s*(a+b))-(15.3*y^2)*(p/s)*(a+b)-(h/s*(a+b))')

drdt=(-m*(r^(((m+1)/m))*z*s))/(n^(((1/m))*v))-(n^(1/m))*k')

yes, I have replaced the variables that exist with the symbol
several variables that are known are abcspjknm
until recently I saw some tutorials and answers from this forum using the syntax 'dsolve'

more or less like this
u=dsolve('Dx=-c*z*s','Dy=((-1.021*(y^2))/(b+a))-(2.081015257+(6.936717523*x))/(b+a)+((p*r)-(p*j)/(b+a))-(((p^2)-2*p*(s^2)*c*z^2))/2*p','Dz=(((p^2)*r)-((p^2)*j))/(((S*x)+((p^2)*r))-((p^2)*j)/(b+a))-(((z^2)*c*(p^2))/(2*s*x))+(((z^2)*c*(s^2))/(2*s*x))-((z^2)*c*((p-s)^2)/2*s*(a+b))-(15.3*y^2)*(p/s)*(a+b)-(h/s*(a+b))','Dq=(-m*(r^(((m+1)/m))*z*s))/(n^(((1/m))*v))-(n^(1/m))*k','x(0)=0','y(0)=0','z(0)=0','r(0)=0')

but the ans is
Warning: Explicit solution could not be found.
> In dsolve at 120

u =

[ empty sym ]

i need clue to solve it,and tell me if iam in the right path.

regards

2. May 20, 2012

### a.gema

-update-
i calculate all equation with known variabels,
and the output compose to dsolve syntax,more or less like this

[x,y,z,r]=dsolve('Dx = -(565939190652381375*z)/1152921504606846976','Dy = (16355638459336405*r)/864691128455135232 - (12667033077522942535719631836275*z^2)/166153499473114484112975882535043072 - (1021*y^2)/300 - (6508374677449415*x)/281474976710656 - 1082834104814639805/562949953421312','Dz = (4751877281217605*r)/147573952589676412928 - (31989963214599364608*x)/7545855875365085 - (25153697399630671875*z^2)/(772695641637384704*x) + (9223372036854775808*((4751877281217605*r)/147573952589676412928 - 1836715566709037/562949953421312))/(4527513525219051*x) - (3339821373396493901*y^2)/943231984420635625 - (2692950552872551939327614513538875*z^2)/1361129467683753853853498429727072845824 - 5448823127243492586999657831994653/4247939213560708089152819691520','Dr = - (4441490768239889031*r^(9811/9810)*z)/924173579960068096 - 2254787716421851/4503599627370496')

but the answer is sill same
any help would be greatly appreciated

regards