how to composite two polynomial in maple

i would like to search a o b = 1

composite two polynomial equal identity

though swap can do this,

hope to know a simple way to shift a list or set to the left in cycle in maple

for example

1,2,3

2,3,1

3,1,2

with(Physics):
L := diff(q2(t), t)
diff(L, q2(t))

it return 0, is it correct?

how to make below can be successfully run?

normaldiff := proc(f1)
return limit((subs(x=x+h,f1)-f1)/h, h=0):
end if:
recurdiff := proc(f2)
if f2 = 0 then
return 0:
end if:
if f2 <> 0 then
return limit((subs(x=x+h,normaldiff(f2)+recurdiff(f2))-(normaldiff(f2)+recurdiff(f2)))/h, h=0):
end if:

f := x;
normaldiff(f)+recurdiff(f);

expect return 1, is like normal diff

and show whether there is sink or source?

ode1:=a(t)*(diff(a(t), t))+c(t)*(diff(c(t), t))=3*t;
ode2:=a(t)*(diff(a(t), t))+a(t)*(diff(a(t), t))*b(t)*(diff(b(t), t))*c(t)*(diff(c(t), t))=3*t;
ode3:=a(t)*(diff(a(t), t))+a(t)*(diff(a(t), t))*c(t)*(diff(c(t), t))+a(t)*(diff(a(t), t))*b(t)*(diff(b(t), t))*c(t)*(diff(c(t), t))=2*t;

DEtools[DEplot3d]({ode1,ode2,ode3},[a(t),b(t),c(t)],t=0.5..1.4,a=0..1.4,b=0..1.4,c=0..1.4,[[a(1)=1,b(1)=2,c(1)=3]],scene=[a(t),b(t),c(t)], arrows=medium);

unable to convert to explicit first order system, do not understand this error message