Laravel :method is defined in controller yet it says method not found

I am using laravl 5.2 and following is my code

I am getting error

ReflectionException in Route.php line 280: Method App\Http\Controllers\Signup_controllers::guestcheckout() does not exist

whats wrong i am doing? plz help

this is my route.php

Route::group(array('prefix' => 'signup'), function()
{
    Route::resource('/register', 'Signup_controllers@register');
    Route::resource('/guestcheckout', 'Signup_controllers@guestcheckout');
    Route::resource('/login', 'Signup_controllers@login');
    Route::resource('/logout', 'Signup_controllers@logout');
    Route::resource('/ajaxCheckCustomerEmailExist', 'Signup_controllers@ajaxCheckCustomerEmailExist');
});

this is my signup controller

    <?php

    namespace App\Http\Controllers;
    use Illuminate\Http\Request;
    use App\Http\Requests;
    use App\Http\Controllers\Controller;
    use Illuminate\Support\Facades\Input;
    use Symfony\Component\HttpFoundation\File\UploadedFile;
    use Symfony\Component\HttpFoundation\Session\Session1;
    use Illuminate\Support\Facades\Validator;
    use Illuminate\Support\Facades\Redirect;
    use Image;
    use Session;
    use DB;
    use Mail;

    use App\Http\Models\Frm_mailing_list;
    use App\Http\Models\Frm_contactus;
    use App\Http\Models\Emailautoresponse;
    use App\Http\Models\Adminemail;
    use App\Http\Models\Emailsetting;
    use App\Http\Models\Product_price;

    class Signup_controllers extends Controller
    {
        public function index(Request $request)
        {

        }
        public function register(Request $request)
        {
            include(public_path().'/app/Http/Controllers/action/register_controllers.php'); 
        }
        public function login(Request $request)
        {
            include(public_path().'/app/Http/Controllers/action/login_controllers.php');    
        }
        public function logout()
        {
            Session::flush();
            return Redirect::away(url('/login-registration'))->send();
        }
        public function guestcheckout(Request  $request)
        {
            include(public_path().'/app/Http/Controllers/action/guestcheckout_controllers.php');    
        }

        public function ajaxCheckCustomerEmailExist(Request $request)    
        {
            //Checked By Ranjit
            $email=$request->email;
            $customerData=array('email'=>$email);
            $Customer=new Customer;

            $resultCustomer=$Customer->getByAttributesQuery($customerData);
            if($resultCustomer['recordCount']>0){
                echo "false";
            }else{
                echo "true";
            }
        }
    }

when i try to call guestcheckout it says method not found even i have defined it

via Chebli Mohamed