[Maxima-discuss] Integral of equation

[Daniel V. <dan...@ya...>]

Hi All,
I have the following code:
declare([a,b,y_a,y_b],constant)$

atvalue(y(x),x=a,y_a)$atvalue(y(x),x=b,y_b)$
assume(a<x,x<b)$

Eq0:'diff(y(x),x,2)=u(x); => 'diff(y(x),x,2) = u(x)
Eq1:integrate(Eq0,x,a,x); => 'diff(y(x),x,1)-'diff(y(a),a,1) = 'integrate(u(x),x,a,x)

Eq2:subst(['diff(y(a),a,1)=y\'(a)],Eq1); => 'diff(y(x),x,1)-'diff(y(a),a,1) = 'integrate(u(x),x,a,x)

The first error is in Eq1, the result contains 'diff(y(a),a,1) which makes no sense.The second error is in Eq2, I'm unable to do the substitution of the error.
If I delete atvalue(y(x),x=a,y_a)$ and run all again the substitution is OK.If I do the integration with limits a and b, then both terms of the left-hand side are incorrect.
Is there any way to fix it?Thanks,
Daniel Volinski