<div class="btn-group">
                <div class="col-md-10">

                <form action="{{action('UsuarioController@show', $usuario_ad)}}" method="post">
                    {{csrf_field()}}
                       <select name="tipo" id="tipo" class=" form-control"  value="{{ old('tipo') }}"  required>
                        @foreach($usuariosOpciones as $id => $usuario_ad)
                          <option value="{{ $id }}">{{ $usuario_ad }}</option>
                       @endforeach
                   </select>
                <a class="btn btn-info" >Buscar</a>
             </form>



                 </div>  
              </div>