WPF Display Math number square, show big character and small character via Textblock run horizontal without space BaselineAlignment="Baseline" BaselineAlignment="Subscript"

//xaml
<Window x:Class="WpfApp37.MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
        xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
        xmlns:local="clr-namespace:WpfApp37"
        mc:Ignorable="d"
        WindowState="Maximized"
        Title="MainWindow" Height="450" Width="800">
    <Window.Resources>
        <Style TargetType="{x:Type TextBlock}">
            <Setter Property="FontSize" Value="50"/>
        </Style>
    </Window.Resources>
    <Grid x:Name="gd">
        <Grid.RowDefinitions>
            <RowDefinition Height="200"/>
            <RowDefinition/>
            <RowDefinition/>
            <RowDefinition/>
            <RowDefinition/>
            <RowDefinition/>
        </Grid.RowDefinitions>
        <TextBlock Grid.Row="0" Text="Quadratic formula: x = (−b ± √(b² − 4ac)) / (2a)" 
                   VerticalAlignment="Center"/>
        <TextBlock Grid.Row="1" Text="R²"/>
        <TextBlock Grid.Row="2">
            <Run Text="K" FontSize="24" BaselineAlignment="Baseline" /><Run Text="D" FontSize="12" BaselineAlignment="Subscript"/>
        </TextBlock>
        <TextBlock Grid.Row="4">
            <TextBlock.Inlines>
                <Run Text="K" FontSize="24" FontWeight = "Bold" BaselineAlignment="Baseline"/><Run Text="D" FontSize="12"  FontWeight = "Bold" BaselineAlignment="Subscript"/>
            </TextBlock.Inlines>
        </TextBlock>
       
    </Grid>
</Window>


//cs
using System.Text;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Data;
using System.Windows.Documents;
using System.Windows.Input;
using System.Windows.Media;
using System.Windows.Media.Imaging;
using System.Windows.Navigation;
using System.Windows.Shapes;

namespace WpfApp37
{
    /// <summary>
    /// Interaction logic for MainWindow.xaml
    /// </summary>
    public partial class MainWindow : Window
    {
        public MainWindow()
        {
            InitializeComponent();

            var textBlock = new TextBlock();
            textBlock.Inlines.Add(new Run("K")
            {
                FontSize = 24,
                FontWeight = FontWeights.Bold
            });
            textBlock.Inlines.Add(new Run("D")
            {
                FontSize = 12,
                FontWeight = FontWeights.Bold,
                BaselineAlignment = BaselineAlignment.Baseline,                
            });
            Grid.SetRow(textBlock, 3);
            gd.Children.Add(textBlock);
        }
    }
}