Bdtyktl

I am trying to reproduce an image. I could probably do alone but it may not be the best way so I am asking what is the fastest and easiest way achieve the result:

documentclass{article}



usepackage{amsmath,tikz}

newcommand{der}[2]{dfrac{d#1}{d#2}}



begin{document}

begin{center}

$begin{aligned}[t]

     &phantom{==}der{}{x} (x^{2} cdot x^{5}) \ \

             &=x^{2} cdot textcolor{red}{5x^{4}}+x^{5} cdot 

 textcolor{red}{2x}\

             &=5x^{6}+2x^{6}\

             &=7x^{6}

end{aligned}$

end{center}

end{document}

This outputs:

I am trying to achieve:

Here's a proposal. It requires the latest version of tikzmark, i.e. should work if you have updated your TeX installation in the past 2 months or so.

documentclass{article}



usepackage{amsmath,tikz}

usetikzlibrary{tikzmark}

newcommand{der}[2]{dfrac{mathrm{d}#1}{mathrm{d}#2}}



begin{document}

begin{center}

$begin{aligned}[t]

     &phantom{==}der{}{x} (x^{2} tikzmarknode{0}{cdot} x^{5}) \[0.8cm]

             &=tikzmarknode{1}{x^{2}} cdot 

             tikzmarknode[red]{2}{5x^{4}}+

             tikzmarknode{3}{x^{5}} tikzmarknode{5}{cdot}

tikzmarknode[red]{4}{2x}\

             &=5x^{6}+2x^{6}\

             &=7x^{6}

end{aligned}$

end{center}

begin{tikzpicture}[overlay,remember picture,cyan!70]

path ([yshift=0.1cm]1.north) coordinate (aux);

foreach X in {1,...,4}

{draw   (X |-aux) node[above,circle,draw,font=small,inner sep=1pt]

(LX){X};}

draw[very thick] ([xshift=-2pt,yshift=2pt]L1.west) |- 

([xshift=2pt,yshift=8pt]L4.east) coordinate (aux2) -- ([xshift=2pt]L4.east);

draw[very thick,-latex] (0.south) -- (0|-aux2);

path ([yshift=-4pt]5.south) node[below,circle,draw,font=small,inner

sep=1pt]{5};

end{tikzpicture}

end{document}

or (it is hard for me to judge where the 5 node should be sitting)

documentclass{article}



usepackage{amsmath,tikz}

usetikzlibrary{tikzmark,positioning}

newcommand{der}[2]{dfrac{mathrm{d}#1}{mathrm{d}#2}}



begin{document}

begin{center}

$begin{aligned}[t]

     &phantom{==}der{}{x} (x^{2} tikzmarknode{0}{cdot} x^{5}) \[0.8cm]

             &=tikzmarknode{1}{x^{2}} cdot 

             tikzmarknode[red]{2}{5x^{4}}+

             tikzmarknode{3}{x^{5}} cdot

tikzmarknode[red]{4}{2x}\

             &=5x^{6}+tikzmarknode{5}{2x^{6}}\

             &=7x^{6}

end{aligned}$

end{center}

begin{tikzpicture}[overlay,remember picture,cyan!70]

path ([yshift=0.1cm]1.north) coordinate (aux);

foreach X in {1,...,4}

{draw   (X |-aux) node[above,circle,draw,font=small,inner sep=1pt]

(LX){X};}

draw[very thick] ([xshift=-2pt,yshift=2pt]L1.west) |- 

([xshift=2pt,yshift=8pt]L4.east) coordinate (aux2) -- ([xshift=2pt]L4.east);

draw[very thick,-latex] (0.south) -- (0|-aux2);

node[right=3pt of 5,circle,draw,font=small,inner sep=1pt]{5};

end{tikzpicture}

end{document}