nt((eq[2] - db2 - eq[0]*(x_min))/eq[1]));
        context.strokeStyle = line_colors[i];
        context.stroke();
        context.closePath();
        context.fillStyle = fill_colors[i];
        context.fill();
    }
    context.globalAlpha = 1.0;
    for(var i = 0; i < solver_1_eqs; ++i){
        var eq = eval("solver_1_eq_" + (i + 1));     
        // line
        context.beginPath();
        context.lineWidth = 2;
        var xys = get_points_on_the_ends(eq[0], eq[1], eq[2]);
        context.moveTo(x_to_