reserve a,b,k,m,n,s for Nat;
reserve c,c1,c2,c3 for Complex;
reserve i,j,z for Integer;
reserve p for Prime;
reserve x for object;
reserve f,g for complex-valued FinSequence;

theorem :: Problem 196 b
  { [x,y,z,t] where x,y,z,t is Integer: x+y = z*t & z+t = x*y } is infinite
  proof
    dom f = NAT by PARTFUN1:def 2;
    hence thesis by Th85,CARD_1:59;
  end;
