Đại 9

C

c2nghiahoalgbg

lược giải này


(2+6)2=8+43<8+44=16(\sqrt{2}+\sqrt{6})^2=8+4\sqrt{3} < 8+4\sqrt{4}=16

\Rightarrow 2\sqrt{2}+6\sqrt{6} < 4

tương tự : 12\sqrt{12}+20\sqrt{20} < 8 ;30 \sqrt{30}+42\sqrt{42} < 12

\Rightarrow 2\sqrt{2}+6\sqrt{6}+12\sqrt{12}+20\sqrt{20}+30\sqrt{30}+42\sqrt{42}< 24(*)(*)(*)(*)(*)
 
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