Laravel 5 Eloquent - query for absense of relationship in model - e.g. retrieve user's unanswered questions

I have User, Answer, and Question models. Answers belong to users and questions, i.e. the answers table has a user_id column and a question_id column.

My User model has a method to return all answered questions

class User extends Model {
    public function answeredQuestions(){
        return $this->hasManyThrough('App\Answer', 'App\Question');
    }
}

I'd like to have another method to retrieve all unanswered questions, but I'm not sure how to go about that. As a workaround I can get it from the Question model by passing in a user id like this:

class Question extends Model {
    public function scopeUnanswered($query, $user_id){
        return $query->whereDoesntHave('answers', function ($query) use ($user_id) {
            $query->where('user_id', $user_id);
        })->get();
    }
}

I would prefer to access it via the User model with $user->unansweredQuestions though. Is this possible to do cleanly through the User model?

via Chebli Mohamed