Unfortunately, I am not so good at extracting single characters from the other fonts, so I would like to ask for some help.
I need to import 'u' and 'v', that are used in math mode, from txfonts
I am aware of this answer, but the solution there corrupts other math characters for me. I guess that is because there is no \DeclareFontFamily and \DeclareFontShape to exclude there.
Here is the code I am using
\documentclass{article}
\usepackage{mathtext}
\usepackage[T2A]{fontenc}
\usepackage[utf8]{inputenc}
\usepackage{amsmath,amsfonts,amssymb,amsthm,mathtools}
\usepackage{mathabx}
\usepackage{polynom}
\usepackage{xparse}
\DeclareFontFamily{OMX}{MnSymbolE}{}
\DeclareFontShape{OMX}{MnSymbolE}{m}{n}{
<-6> MnSymbolE5
<6-7> MnSymbolE6
<7-8> MnSymbolE7
<8-9> MnSymbolE8
<9-10> MnSymbolE9
<10-12> MnSymbolE10
<12-> MnSymbolE12}{}
\DeclareFontShape{OMX}{MnSymbolE}{b}{n}{
<-6> MnSymbolE-Bold5
<6-7> MnSymbolE-Bold6
<7-8> MnSymbolE-Bold7
<8-9> MnSymbolE-Bold8
<9-10> MnSymbolE-Bold9
<10-12> MnSymbolE-Bold10
<12-> MnSymbolE-Bold12}{}
\DeclareSymbolFont{mnlargesymbols}{OMX}{MnSymbolE}{m}{n}
\SetSymbolFont{largesymbols}{bold}{OMX}{MnSymbolE}{b}{n}
\DeclareMathDelimiter{\lwavy}{\mathopen}{mnlargesymbols}{'136}{mnlargesymbols}{'136}
\DeclareMathDelimiter{\rwavy}{\mathclose}{mnlargesymbols}{'136}{mnlargesymbols}{'136}
% --- Get fancy 'u' and 'v' --- %
\DeclareSymbolFont{matha}{OML}{txmi}{m}{it}
\DeclareMathSymbol{\varru}{\mathord}{matha}{117}
\DeclareMathSymbol{\varrv}{\mathord}{matha}{118}
\begin{document}
\begin{gather*}
\lambda^3-\lambda^2-5\lambda-3 = 0,\\
(\lambda+1)(\lambda^2-2\lambda-3) = 0,\\
(\lambda+1)(\lambda+1)(\lambda-3) = (\lambda+1)^2(\lambda-3) = 0,\\
\lambda_{1\,[2]}=-1, \qquad \lambda_{2\,[1]} = 3
\\
\\
f(u) = u^2+3u
\end{gather*}
\end{document}
And also I would like to use them nativly, so that I don't need a command for them like \varu, \varv,
simply use it straight forward f(u) = u^2 + 3u


