Am i using "this->" correctly?

I am developing a c++ program for a Calculus homework, but i am getting a compilation error when i declare the "grafico" instance of "Grafico" class inside the "EDO" class. I am not so used to using C++, so could you guys help me find out what i am missing? Am i properly using "this->"?

Here is the main code for the problem (The comments are in portuguese so you can ignore they):

class Grafico {
    public:
        Grafico(std::vector<double>& x, std::vector<double>& y) {
            xValues = x;
            yValues = y;
        }
        ~Grafico(){}
        void plotar() {
            plt::plot(this->xValues, this->yValues, "o-");
            plt::title(this->titulo);
            plt::show();
        }

    private:
        std::vector<double> xValues, yValues;
        const std::string titulo = "Solução Numérica";
};

class EDO {
    public:
        double f(double x, double y) {
            return 2*y/(x+1) + std::pow(x+1, 3);
        }
        double get_x0() {
            return this->x_0;
        }
        double get_y0() {
            return this->y_0;
        }
        void adicionar_ponto(double x, double y) {
            this->x.push_back(x);
            this->y.push_back(y);
        }
        void plotar_grafico() {
            this->grafico.plotar();
        }
    private:
        const double x_0=0, y_0=3; // Valores iniciais
        std::vector<double> x {this->x_0};
        std::vector<double> y {this->y_0}; // Pontos da função resultante
        Grafico grafico(this.x,this.y);
};

And here is the error i get when compiling using g++ and c++11: