demo/subst.dem

   1 eq1:3*x^4+2*x^2=7;
   2 sbst:x^2=u;
   3
   4 subst(sbst,eq1);
   5
   6 eq2:subst(last(solve(sbst,x)),eq1);
   7 eq3:solve(eq2,u);
   8
   9 subst(solve(sbst,u),eq3);
  10
  11 subst([a=b,b=c,c=d],[a+b+c+d]);
  12
  13 psubst([a=b,b=c,c=d],[a+b+c+d]);
  14
  15 eq4:f_res=1/(2*π*sqrt(L*C));
  16
  17 circuit1:[L=1e-3,C=100e-12];
  18 circuit2:[L=10e-3,C=1e-12];
  19
  20 float(subst(circuit1,eq4));
  21
  22 float(subst(circuit2,eq4));