code: function(eq) {
              var lhs = new Symbol(0),
                  rhs = new Symbol(0);
              eq.each(function(x) {
                  if(x.contains(solve_for, true))
                      lhs = _.add(lhs, x.clone());
                  else
                      rhs = _.subtract(rhs, x.clone());
              });
              return [lhs, rhs];
          }
docs: separate the equation