let
[tex]A=(\sqrt{2} +\sqrt{3} )(\sqrt{4} +\sqrt{5} )...(\sqrt{2020} +\sqrt{2021} )\\B=(\sqrt{2021} -\sqrt{2020} )(\sqrt{2019} -\sqrt{2018} )...(\sqrt{3} -\sqrt{2} )[/tex]
what is A times B?