Solve for diff(e2, x, 1) after x and d have been reassigned new values after e4 at e5.

I'm still not sure what you are trying to do, but maybe something like the following will help you
get started:

 (%i21) depends(y,[x,d])$
 (%i22) x^2+d*y*4+d^2*(-4)$
 
 (%i23) first(solve(x^2+d*y*4+d^2*(-4),y));
 (%o23) y=-(x^2-4*d^2)/(4*d)

 (%i24) map(lambda([s], at(s, [x=50, d=25])),[diff(%,x), diff(%,d)]);
 (%o24) [at('diff(y,x,1),[x=50,d=25])=-1,at('diff(y,d,1),[x=50,d=25])=2]

Maybe more simple:

 (%i1) x^2+d*y*4+d^2*(-4)$

 (%i2) rhs(first(solve(x^2+d*y*4+d^2*(-4),y)));
 (%o2) -(x^2-4*d^2)/(4*d)

 (%i3) subst([x=50, d=25],[diff(%,x), diff(%,d)]);
 (%o3) [-1,2]

--Barton

-----maxima-bounces at math.utexas.edu wrote: -----


>To?start?over?again?the?issue?is?to?Solve?for?
>diff(e2,x,1)
>
>after?
>x
>?and?
>d
>?have?been?reassigned?new?values?after?
>e4?at?e5
>.
>
>
>
>?
>
>
>(%i1)?e1:?x^2+d*y*4+d^2*(-4);
>
>
>
>???????????????????????????????????????????
>2??????2
>
>
>
>(%o1)?????????????????????????
>4?d?y?+?x??-?4?d
>
>
>
>(%i2)?e2:?solve(e1,?y);
>
>
>
>???????????????????????????????????????????????
>2??????2
>
>
>
>?????????????????????????????
>????????????????x?
>-?4?d
>
>
>
>(%o2)?????????????????????????
>[y?=?-?---------]
>
>
>
>????????????????????????????????????????????????
>4?d
>
>
>
>(%i3)?e3:?subst([y=0,?d=5],?e1);
>
>
>
>?????????????????????????????????????????
>2
>
>
>
>(%o3)?????????????????????????????
>x??-?100
>
>
>
>(%i4)?e4:?solve(e3,?x);
>
>
>
>(%o4)????????????????????????
>[x?=?-?10,?x?=?10]
>
>
>
>(%i5)?e5:?subst([x=50,?d=25],?e2);
>
>
>
>(%o5)??????????????????????????????
>[y?=?0]
>
>
>
>?
>
>
>So?at?this?point?x=-10?and?10?when
>y=0…
>
>
>
>Now?e4?has?been?reassigned?new
>values?at?e5,?x=50?and?d=50.?If?I?write?e6:?solve(e5,x);?which?gives?me
>[].?Now
>when?I?continue?to?solve?and?assign?as?follows…
>
>
>
>?
>
>
>(%i6)?e6:?solve(e5,x);
>
>
>
>(%o6)???????????????????????????????
>[]
>
>
>
>(%i7)?e7:?diff(e2,x,1);
>
>
>
>????????????????????????????????????????????????
>x
>
>
>
>(%o7)???????????????????????????
>[0?=?-?---]
>
>
>
>??????????????????????????????????????????????
>2?d
>
>
>
>(%i8)?%phi[1]?:?e7;
>
>
>
>????????????????????????????????????????????????
>x
>
>
>
>(%o8)???????????????????????????
>[0?=?-?---]
>
>
>
>??????????????????????????????????????????????
>2?d
>
>
>
>(%i9)?%phi[2]?:?e7;
>
>
>
>?????????
>???????????????????????????????????????x
>
>
>
>(%o9)???????????????????????????
>[0?=?-?---]
>
>
>
>??????????????????????????????????????????????
>2?d
>
>
>
>Now?when?I?execute…
>
>
>
>(%i10)?subst([e6[1],
>d=25],%phi[1]);?
>
>
>
>(%i11)?subst([e6[2],
>d=25],%phi[2]);
>
>
>
>I?get?“Improper?index?to?list
>or?matrix?–?an?error.
>
>
>
>?
>
>
>The?values?I?should?have?for?(%i10)
>and?(%i11)?should?be?1.0?and?-1.0.?The?purpose?of?this?set?of?expressions
>is?to
>be?able?to?reassign?values?to?
>x
>?and?
>d
>?and?wind?up?with?the
>derivative?values?of?(%i2).
>
>
>
>?
>
>
>William?Porter
>
>
>
>wporter at omegapar.com
>
>
>
>
>
>?
>
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