Laravel.io
<div class="btn-group">
                <div class="col-md-6">
                             <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>

                         <form action="{{route('usuario.show', $id)}}" method="POST">
                               {{csrf_field()}}
                              
                            <a class="btn btn-info" >Buscar</a>
                        </form>
                        
                   
                 </div>  
              </div>

Please note that all pasted data is publicly available.