Width = 2;
        var xys = get_points_on_the_ends(eq[0], eq[1], eq[2]);
        context.moveTo(x_to_client(xys[0][0]), y_to_client(xys[0][1]));
        context.lineTo(x_to_client(xys[1][0]), y_to_client(xys[1][1]));
        context.strokeStyle = line_colors[i];
        context.stroke();
        context.lineWidth = 1;
        context.closePath();
    }

    // solver
    context.beginPath();
    context.moveTo(x_to_client(0), y_to_client(0));
    var ixy = solve_2(solver_1_eq_1[0], solver_1_eq_1[1], 0,  so