kill(all);

mxref:F*l/b;
kxref:12*F*l/E/b/h^3;

D:E/(1-ν^2)*matrix([1,ν,0],[ν,1,0],[0,0,(1-ν)/2]);

c:h^3/12*D;

matrix([mx],[my],[mxy])-c.matrix([kx],[ky],[kxy]);

eqns:[%[1][1],%[2][1]];

linsolve(eqns,[kx,ky]),[mx=mxref,my=0];
ratsubst('kxref,kxref,%)$
ratsubst('mxref,mxref,%)$
factor(%);

linsolve(eqns,[kx,my]),[mx=mxref,ky=0];
ratsubst('kxref,kxref,%)$
ratsubst('mxref,mxref,%)$
factor(%);