X[2].toFixed(2) + "x<sup>2</sup> + " + X[1].toFixed(2) + "x + " + X[0].toFixed(2);

    // back
    synthesis_context.beginPath();
    for(var j = 1; j < w; ++j){
        x1 = client_to_x(j-1);
        x2 = client_to_x(j);
        y1 = polynomial_in_x(X, x1, synthesis_n);
        y2 = polynomial_in_x(X, x2, synthesis_n);
        synthesis_context.moveTo(x_to_client(x1), y_to_client(y1));
        synthesis_context.lineTo(x_to_client(x2), y_to_client(y2));
    }
    synthesis_context.strokeStyle="#FF9988";
  