Hi everyone,

I am trying to solve the problem described below and it has been runing for days without solving it.

What can I do?
 
Thanks for your help.

Problem:

eq1 := (1/1152)*(81*a1*P^4*b^4*C1^3+162*a1*P^4*b^4*C1*C2^2+648*a1*P^4*b^4*C1*C3^2+432*a1*P^4*b^4*C1*C4^2+864*a1*P^4*b^4*C2*C3*C4+18*a2*P^4*a^2*b^2*C1^3+90*a2*P^4*a^2*b^2*C1*C2^2+90*a2*P^4*a^2*b^2*C1*C3^2+288*a2*P^4*a^2*b^2*C1*C4^2+81*a3*P^4*a^4*C1^3+648*a3*P^4*a^4*C1*C2^2+162*a3*P^4*a^4*C1*C3^2+432*a3*P^4*a^4*C1*C4^2+864*a3*P^4*a^4*C2*C3*C4+288*d1*P^4*b^4*C1+576*d2*P^4*a^2*b^2*C1+288*d3*P^4*a^4*C1+1152*d4*P^4*a^2*b^2*C1+4096*Tc*a^3*b^3*C4)/(b^3*a^3) = 0;

eq2 := (1/1152)*(162*a1*P^4*b^4*C1^2*C2+864*a1*P^4*b^4*C1*C3*C4+81*a1*P^4*b^4*C2^3+432*a1*P^4*b^4*C2*C3^2+648*a1*P^4*b^4*C2*C4^2+90*a2*P^4*a^2*b^2*C1^2*C2+72*a2*P^4*a^2*b^2*C2^3+612*a2*P^4*a^2*b^2*C2*C3^2+360*a2*P^4*a^2*b^2*C2*C4^2+648*a3*P^4*a^4*C1^2*C2+864*a3*P^4*a^4*C1*C3*C4+1296*a3*P^4*a^4*C2^3+432*a3*P^4*a^4*C2*C3^2+2592*a3*P^4*a^4*C2*C4^2+288*d1*P^4*b^4*C2+2304*d2*P^4*a^2*b^2*C2+4608*d3*P^4*a^4*C2+4608*d4*P^4*a^2*b^2*C2-4096*Tc*a^3*b^3*C3)/(b^3*a^3) = 0;

eq3 := (1/1152)*(648*a1*P^4*b^4*C1^2*C3+864*a1*P^4*b^4*C1*C2*C4+432*a1*P^4*b^4*C2^2*C3+1296*a1*P^4*b^4*C3^3+2592*a1*P^4*b^4*C3*C4^2+90*a2*P^4*a^2*b^2*C1^2*C3+612*a2*P^4*a^2*b^2*C2^2*C3+72*a2*P^4*a^2*b^2*C3^3+360*a2*P^4*a^2*b^2*C3*C4^2+162*a3*P^4*a^4*C1^2*C3+864*a3*P^4*a^4*C1*C2*C4+432*a3*P^4*a^4*C2^2*C3+81*a3*P^4*a^4*C3^3+648*a3*P^4*a^4*C3*C4^2+4608*d1*P^4*b^4*C3+2304*d2*P^4*a^2*b^2*C3+288*d3*P^4*a^4*C3+4608*d4*P^4*a^2*b^2*C3-4096*Tc*a^3*b^3*C2)/(b^3*a^3) = 0;

eq4 := (1/144)*(54*a1*P^4*b^4*C1^2*C4+108*a1*P^4*b^4*C1*C2*C3+81*a1*P^4*b^4*C2^2*C4+324*a1*P^4*b^4*C3^2*C4+162*a1*P^4*b^4*C4^3+36*a2*P^4*a^2*b^2*C1^2*C4+45*a2*P^4*a^2*b^2*C2^2*C4+45*a2*P^4*a^2*b^2*C3^2*C4+36*a2*P^4*a^2*b^2*C4^3+54*a3*P^4*a^4*C1^2*C4+108*a3*P^4*a^4*C1*C2*C3+324*a3*P^4*a^4*C2^2*C4+81*a3*P^4*a^4*C3^2*C4+162*a3*P^4*a^4*C4^3+576*d1*P^4*b^4*C4+1152*d2*P^4*a^2*b^2*C4+576*d3*P^4*a^4*C4+2304*d4*P^4*a^2*b^2*C4+512*Tc*a^3*b^3*C1)/(b^3*a^3) = 0;

solve({eq1, eq2, eq3, eq4}, {C1, C2, C3, C4});

I want to solve the problem described below. I tried using two methods as shown below, each method has been runing for days without solving it. I will really appreciate your help.

Det1 := (1/256)*(Aiso*(c+t)^2*(a^2+b^2)*(mu-1)*Pi^2-4*a^2*b^2*c*Gc)*(16*Aiso^2*Do^2*(c+t)^4*(a^2+b^2)^6*Pi^12+10*(a^2+b^2)^5*((c+t)^2*Aiso+4*Do)*Gc*(c+t)^2*c*a^2*Do*b^2*Aiso*Pi^10+(a^2+b^2)^4*((c+t)^2*Aiso+4*Do)^2*Gc^2*c^2*a^4*b^4*Pi^8-(1024/81)*a^6*Aiso^2*b^6*Tcr^2*(c+t)^4*(a^2+b^2)^2*Pi^4-(2560/81)*a^8*Aiso*b^8*c*Gc*Tcr^2*(c+t)^2*(a^2+b^2)*Pi^2-(1024/81)*a^10*b^10*c^2*Gc^2*Tcr^2)*(Aiso*(c+t)^2*(a^2+4*b^2)*(mu-1)*Pi^2-4*a^2*b^2*c*Gc)*(Aiso*(c+t)^2*(a^2+b^2)*(mu-1)*Pi^2-a^2*b^2*c*Gc)*(16*(c+t)^4*(a^2+(1/4)*b^2)^3*Do^2*(a^2+4*b^2)^3*Aiso^2*Pi^12+(10*(a^2+b^2))*((c+t)^2*Aiso+4*Do)*Gc*(c+t)^2*(a^2+(1/4)*b^2)^2*c*a^2*Do*(a^2+4*b^2)^2*b^2*Aiso*Pi^10+((c+t)^2*Aiso+4*Do)^2*Gc^2*(a^2+(1/4)*b^2)^2*c^2*a^4*(a^2+4*b^2)^2*b^4*Pi^8-(1024/81)*(c+t)^4*(a^2+(1/4)*b^2)*Tcr^2*a^6*(a^2+4*b^2)*b^6*Aiso^2*Pi^4-(2560/81)*a^8*Aiso*b^8*c*Gc*Tcr^2*(c+t)^2*(a^2+b^2)*Pi^2-(1024/81)*a^10*b^10*c^2*Gc^2*Tcr^2)*((mu-1)*(c+t)^2*(a^2+(1/4)*b^2)*Aiso*Pi^2-a^2*b^2*c*Gc)/(b^20*a^20*(c+t)^16) = 0;

# method 1;
EQN := RootOf(Det1, Tcr);

EQN_2 := allvalues(EQN);

# method 2;

EQN := solve(Det1, Tcr);

Please, I need assistance with this problem.

Here is the problem I am trying to solve:

restart:
with(plots):
with(LinearAlgebra):
with(PDEtools):
with(Student):

myPDE1 := D11*diff(w(x,y), x$4) + 2*(D12+2*D66)*diff(w(x,y), y$4) + D22*diff(w(x,y), x$2, y$2) - G*diff(w(x,y), x,y)= 0;

pdsolve(myPDE1);

pdsolve(myPDE1, build);

"Boundary conditions";
"(Note:the domain for the problem is a rectangle)";
bc1 := w(0,y) = 0; # @ x=0 edge;
bc2 := w(a,y) = 0;  # @ x=a edge;
bc3 := w(x,0) = 0; # @ y=0 edge;
bc4 := w(x,b) = 0; # @ y=b edge;
bcx1 := -D11*D[2](w)(0,y) - D12*D[2](w)(0,y) = 0; # @ x=0 edge;
bcx2 := -D11*D[2](w)(a,y) - D12*D[2](w)(a,y) = 0; # @ x=a edge;
bcy1 := -D12*D[2](w)(x,0) - D22*D[2](w)(x,0) = 0; # @ y=0 edge;
bcy2 := -D12*D[2](w)(x,b) - D22*D[2](w)(x,b) = 0; # @ y=b edge;

sol := [myPDE1, bc1, bc2, bc3, bc4, bcx1, bcx2, bcy1, bcy2];

pdsolve(sol);

"Note:
and D11, D12, D22, D66 and G are constant.
The intention is to find the critical value for G"

I need help with how I can handle the boundary conditions for the problem. Thanks a million.