kill(all)$

van=facebook.com/LearningCalculus$

f(x,y):=5*x^2-5*y^2-2*xy-11=0$

g(x,y):=x^2+y^2+10*x*y-23=0$

s:solve((f(x,y),g(x,y)),[x,y])$

subst(b, %r2, subst(a,%r1,s));