a ) Ta có : \(\left\{{}\begin{matrix}\sqrt{2}< \sqrt{3}\\\sqrt{11}< \sqrt{16}\end{matrix}\right.\Rightarrow\sqrt{2}+\sqrt{11}< \sqrt{3}+4\)
b ) Ta có : \(\left\{{}\begin{matrix}\sqrt{21}>\sqrt{20}\\-\sqrt{5}>-\sqrt{6}\end{matrix}\right.\Rightarrow\sqrt{21}-\sqrt{5}>\sqrt{20}-\sqrt{6}\)
c ) Ta có : \(\sqrt{24}< \sqrt{25}\Rightarrow\sqrt{24}-1< \sqrt{25}\Rightarrow\sqrt{24}-1< 5\)