Expression Error in Document format XML

Public Sub SetMainDocumentContent2(ByVal part As MainDocumentPart)

        Const docXml As String = "<?xml version=""1.0"" encoding=""UTF-8"" standalone=""yes""?>" & _
  "<w:document xmlns:ve=""http://schemas.openxmlformats.org/markup-compatibility/2006"">" & _
 "<xmlns:o=""urn:schemas-microsoft-com:office:office"">" & _
 "<xmlns : r = ""http://schemas.openxmlformats.org/officeDocument/2006/relationships"">" & _
 "<xmlns:m=""http://schemas.openxmlformats.org/officeDocument/2006/math"">" & _
 "<xmlns:v=""urn:schemas-microsoft-com:vml"">" & _
 "<xmlns:wp=""http://schemas.openxmlformats.org/drawingml/2006/wordprocessingDrawing"">" & _
 "<xmlns:w10=""urn:schemas-microsoft-com:office:word"">" & _
 "<xmlns:w=""http://schemas.openxmlformats.org/wordprocessingml/2006/main"">" & _
 "<xmlns:wne=""http://schemas.microsoft.com/office/word/2006/wordml"">" & _
 <w:body><w:p w:rsidR="00D45FD9" w:rsidRDefault="001F2E8F"><m:oMathPara><m:oMath><m:sSup><m:sSupPr><m:ctrlPr><w:rPr><w:rFonts w:ascii="Cambria Math" w:hAnsi="Cambria Math"/></w:rPr></m:ctrlPr></m:sSupPr><m:e><m:d><m:dPr><m:ctrlPr><w:rPr><w:rFonts w:ascii="Cambria Math" w:hAnsi="Cambria Math"/></w:rPr></m:ctrlPr></m:dPr><m:e><m:r><w:rPr><w:rFonts w:ascii="Cambria Math" w:hAnsi="Cambria Math"/></w:rPr><m:t>x+a</m:t></m:r></m:e></m:d></m:e><m:sup><m:r><w:rPr><w:rFonts w:ascii="Cambria Math" w:hAnsi="Cambria Math"/></w:rPr><m:t>n</m:t></m:r></m:sup></m:sSup><m:r><w:rPr><w:rFonts w:ascii="Cambria Math" w:eastAsia="Cambria Math" w:hAnsi="Cambria Math" w:cs="Cambria Math"/></w:rPr><m:t>=</m:t></m:r><m:nary><m:naryPr><m:chr m:val="∑"/><m:grow m:val="on"/><m:ctrlPr><w:rPr><w:rFonts w:ascii="Cambria Math" w:hAnsi="Cambria Math"/></w:rPr></m:ctrlPr></m:naryPr><m:sub><m:r><w:rPr><w:rFonts w:ascii="Cambria Math" w:eastAsia="Cambria Math" w:hAnsi="Cambria Math" w:cs="Cambria Math"/></w:rPr><m:t>k=0</m:t></m:r></m:sub><m:sup><m:r><w:rPr><w:rFonts w:ascii="Cambria Math" w:eastAsia="Cambria Math" w:hAnsi="Cambria Math" w:cs="Cambria Math"/></w:rPr><m:t>n</m:t></m:r></m:sup><m:e><m:d><m:dPr><m:ctrlPr><w:rPr><w:rFonts w:ascii="Cambria Math" w:hAnsi="Cambria Math"/></w:rPr></m:ctrlPr></m:dPr><m:e><m:f><m:fPr><m:type m:val="noBar"/><m:ctrlPr><w:rPr><w:rFonts w:ascii="Cambria Math" w:hAnsi="Cambria Math"/></w:rPr></m:ctrlPr></m:fPr><m:num><m:r><w:rPr><w:rFonts w:ascii="Cambria Math" w:eastAsia="Cambria Math" w:hAnsi="Cambria Math" w:cs="Cambria Math"/></w:rPr><m:t>n</m:t></m:r></m:num><m:den><m:r><w:rPr><w:rFonts w:ascii="Cambria Math" w:eastAsia="Cambria Math" w:hAnsi="Cambria Math" w:cs="Cambria Math"/></w:rPr><m:t>k</m:t></m:r></m:den></m:f></m:e></m:d><m:sSup><m:sSupPr><m:ctrlPr><w:rPr><w:rFonts w:ascii="Cambria Math" w:hAnsi="Cambria Math"/></w:rPr></m:ctrlPr></m:sSupPr><m:e><m:r><w:rPr><w:rFonts w:ascii="Cambria Math" w:eastAsia="Cambria Math" w:hAnsi="Cambria Math" w:cs="Cambria Math"/></w:rPr><m:t>x</m:t></m:r></m:e><m:sup><m:r><w:rPr><w:rFonts w:ascii="Cambria Math" w:eastAsia="Cambria Math" w:hAnsi="Cambria Math" w:cs="Cambria Math"/></w:rPr><m:t>k</m:t></m:r></m:sup></m:sSup><m:sSup><m:sSupPr><m:ctrlPr><w:rPr><w:rFonts w:ascii="Cambria Math" w:hAnsi="Cambria Math"/></w:rPr></m:ctrlPr></m:sSupPr><m:e><m:r><w:rPr><w:rFonts w:ascii="Cambria Math" w:eastAsia="Cambria Math" w:hAnsi="Cambria Math" w:cs="Cambria Math"/></w:rPr><m:t>a</m:t></m:r></m:e><m:sup><m:r><w:rPr><w:rFonts w:ascii="Cambria Math" w:eastAsia="Cambria Math" w:hAnsi="Cambria Math" w:cs="Cambria Math"/></w:rPr><m:t>n-k</m:t></m:r></m:sup></m:sSup></m:e></m:nary></m:oMath></m:oMathPara></w:p><w:sectPr w:rsidR="00D45FD9" w:rsidSect="00D45FD9"><w:pgSz w:w="12240" w:h="15840"/><w:pgMar w:top="1440" w:right="1440" w:bottom="1440" w:left="1440" w:header="720" w:footer="720" w:gutter="0"/><w:cols w:space="720"/><w:docGrid w:linePitch="360"/></w:sectPr></w:body></w:document>



        Dim stream1 As Stream = part.GetStream
        Dim utf8encoder1 As UTF8Encoding = New UTF8Encoding()
        Dim buf() As Byte = utf8encoder1.GetBytes(Docxml)
        stream1.Write(buf, 0, buf.Length)
    End Sub