<repositories>
   <repository>
      <id>com.e-iceblue</id>
      <name>e-iceblue</name>
      <url>https://repo.e-iceblue.com/nexus/content/groups/public/</url>
   </repository>
</repositories>
<dependencies>
   <dependency>
      <groupId>e-iceblue</groupId>
      <artifactId>spire.doc.free</artifactId>
      <version>5.2.0</version>
   </dependency>
</dependencies>

import com.spire.doc.*;
import com.spire.doc.documents.Paragraph;
import com.spire.doc.fields.omath.OfficeMath;

public class AddEquation {
    public static void main(String[] args) {
        //Create a Document instance
        Document doc = new Document();

        //Add a section
        Section section = doc.addSection();

        //Add 2 paragraphs and then add Latex Math code to them
        Paragraph paragraph1 = section.addParagraph();
        OfficeMath officeMath1 = new OfficeMath(doc);
        paragraph1.getItems().add(officeMath1);
        officeMath1.fromLatexMathCode("$f(x, y) = 100 * \\lbrace[(x + y) * 3] - 5\\rbrace$");

        Paragraph paragraph2 = section.addParagraph();
        OfficeMath officeMath2 = new OfficeMath(doc);
        paragraph2.getItems().add(officeMath2);
        officeMath2.fromLatexMathCode("$S=a_{1}^2+a_{2}^2+a_{3}^2$");

        //Add another paragraph and then add MathMLCode to it
        Paragraph paragraph3 = section.addParagraph();
        OfficeMath officeMath3 = new OfficeMath(doc);
        paragraph3.getItems().add(officeMath3);
        officeMath3.fromMathMLCode("<mml:math xmlns:mml=\"http://www.w3.org/1998/Math/MathML\" xmlns:m=\"http://schemas.openxmlformats.org/officeDocument/2006/math\"><mml:msup><mml:mrow><mml:mi>x</mml:mi></mml:mrow><mml:mrow><mml:mn>2</mml:mn></mml:mrow></mml:msup><mml:mo>+</mml:mo><mml:msqrt><mml:msup><mml:mrow><mml:mi>x</mml:mi></mml:mrow><mml:mrow><mml:mn>2</mml:mn></mml:mrow></mml:msup><mml:mo>+</mml:mo><mml:mn>1</mml:mn></mml:msqrt><mml:mo>+</mml:mo><mml:mn>1</mml:mn></mml:math>");

        //Save the document
        doc.saveToFile("addMathEquation.docx", FileFormat.Docx_2013);
        doc.dispose();
    }
}