ta có :
\(\sqrt{21}\)>\(\sqrt{20}\)
\(\sqrt{6}\)>\(\sqrt{5}\)
=>\(\sqrt{21}\)+\(\sqrt{6}\)>\(\sqrt{20}\)+\(\sqrt{5}\)
=>\(\sqrt{21}\)-\(\sqrt{5}\)>\(\sqrt{20}\)-\(\sqrt{6}\)(chuyển vế ý mà :D)
vậy ...
\(21>20\Rightarrow\sqrt{21}>\sqrt{20}\)
\(5\sqrt{20}-\sqrt{6}\)
Ta có \(\sqrt{21}-\sqrt{20}>0\)
\(\sqrt{5}-\sqrt{6}\sqrt{5}-\sqrt{6}\)
\(\Rightarrow\sqrt{21}-\sqrt{5}>\sqrt{20}-\sqrt{6}\)
\(\sqrt{21}-\sqrt{5}>\sqrt{21}-\sqrt{6}>\sqrt{20}-\sqrt{6}\)
