[tex]\it a= 2\sqrt2= \sqrt{2^2\cdot2} =\sqrt{8}
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b=\sqrt{18}
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\sqrt{18} \ \textgreater \ \sqrt{8} \Rightarrow b \ \textgreater \ a[/tex]
[tex]\it \ a = 5\sqrt{243} =5\sqrt{81\cdot3} =5\cdot9\sqrt3 =45\sqrt3
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b=27\sqrt{27} =27\sqrt{9\cdot3} =27\cdot3\sqrt3 =81\sqrt3
\\\;\\
81\sqrt3\ \textgreater \ 45\sqrt3 \Longrightarrow b\ \textgreater \ a[/tex]
