Hello guys.

I have a system of differential equations , which I want to solve the perturbation method , but the following problem :

I got zero approximation

**SYS0 := dsolve({Sys, isc}, {delta0(x), u0(x)}, type = numeric, output = listprocedure)**

**SYS0:=[x=proc(x) ... end proc,delta0(x)=proc(x) ... end proc,u0(x)=proc(x) ... end proc]**

How can I use the zero-order approximation for the future is being computed ?

I tried to do so:

**F := eval(delta0(x), SYS0);**

**F1 := eval(u0(x), SYS0);**

**Fdiff := eval(diff(delta0(x), x), SYS0);**

**F1diff := eval(diff(u0(x), x), SYS0);**

Error, (in eval/diff) non-algebraic expressions cannot be differentiated

**Sysq := ((9/10)*F1(x)*F(x)*F1diff-(3/10)*Fdiff*F1(x)*F1(x)+(3/2)*F1(x))*F(x) = (1/5)*F(x)*delta1(x)-(3/10)*u1(x);**

**Sysqq := u1(x)*Fdiff+F1(x)*(diff(delta1(x), x))+delta1(x)*F1diff+F(x)*(diff(u1(x), x)) = 0;**

**SystemSec := Sysq, Sysqq;**

**SYS22 := dsolve({SystemSec, delta1(0) = 10^(-8), u1(0) = 10^(-8)}, {delta1(x), u1(x)}, type = numeric);**

but I can not differentiate u0 (x), delta0 (x) to find u1 (x), delta1 (x) in my system

123.mw

Sorry for my english

Thank