How to transformate the value of solve to the others equation?







Dear All
 1. How to transformate value of solve to the others equation?
  
   eq1 and eq2 is group (1) 
   eq3 and eq4 is group (2)
   
    eq1:x-6y=1        eq3:x+y=-6
    eq2:ax-by=1       eq4:ax+by=-1

they have the some solution.  Solving the a=?, b=?
We have transformate the solution of (eq1 and eq3) into 
(eq2 and eq4) can solve a=?, b=?   

How can I transformate x,y (don't reassign [x,y]:[5,-1]) 
into (eq2 and eq4) directly and solve a,b?


========code==================
kill(all);
powerdisp:true;
eq1:x-6*y=1;
eq2:a*x-b*y=1;
eq3:x+y=-6;
eq4:a*x+b*y=-1;
tmp:solve([eq1,eq3]);
tmp[1][1];
tmp[1][2];

/*[x,y]:[-5,-1];*/ /* reassign x=5,y=-1 , for later use */
eq2(x,y):=a*x-b*y=1;
eq2(x,y);
eq4(x,y):=a*x+b*y=-1;
eq4(x,y);
solve([eq2(x,y),eq4(x,y)]);
===============================
=====running=======
.....
(%i6) tmp:solve([eq1,eq3])
(%o6) [[y=-1,x=-5]]
(%i7) (tmp[1])[1]
(%o7) y=-1
(%i8) (tmp[1])[2]
(%o8) x=-5
(%i9) eq2(x,y):=a*x-b*y=1
(%o9) eq2(x,y):=a*x-b*y=1
(%i10) eq2(x,y)(%o10) a*x-b*y=1
(%i11) eq4(x,y):=a*x+b*y=-1
(%o11) eq4(x,y):=a*x+b*y=-1
(%i12) eq4(x,y)
(%o12) a*x+b*y=-1
(%i13) solve([eq2(x,y),eq4(x,y)])
More unknowns than equations - `solve'
Unknowns given :  [y,b,x,a]
Equations given:  [a*x-b*y=1,a*x+b*y=-1] -- an error.  
To debug this try debugmode(true);


2. How to reassign one of col of maxtrix?
   we have d is a constant item,  
   we want to change the some col of D, 
   such that col(D,1)=d, Dx=D.
         col(D,2)=d, Dy=D.
         col(D,3)=d, Dz=D.
             
   How can I to do?
========= code =======================
r1:[2,-1,1,0];
r2:[1,a,2,2];
r3:[1,2,b,-2];
for i:1 thru 4 do (c[i]:[r1[i],r2[i],r3[i]]);
d:transpose(matrix(c[4]));
tmp:matrix(c[1],c[2],c[3]);
D:transpose(tmp);
col(D,2):d;
Dx:D;
==================================

======= error message ==============
(%i20) col(D,2):d
Improper value assignment:col(D,2) -- an error.  
To debug this try debugmode(true);

 		 	   		  
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