3+2V2 lớn hơn

\(\frac{-4}{3}=\frac{-28}{21};\frac{9}{-7}=\frac{-27}{21}\Rightarrow\frac{-4}{3}

a ) \(2\sqrt{5}-5\) và \(\sqrt{5}-3\)

Ta có ; \(2\sqrt{5}-5-\left(\sqrt{5}-3\right)\)

         \(=\sqrt{5}-8\)

         \(=\sqrt{5}-\sqrt{64}< 0\)

\(\Rightarrow2\sqrt{5}-5< \sqrt{5}-3\)

Vậy .................

b ) \(\sqrt{17}+\sqrt{26}\) và 9 

Ta có : 

\(\sqrt{17}>\sqrt{16}\)

\(\sqrt{26}>\sqrt{25}\)

\(\Rightarrow\sqrt{17}+\sqrt{26}>\sqrt{16}+\sqrt{25}=4+5=9\)

Vậy ...

ta có \(\frac{3}{7}=\frac{27}{63}\); \(\frac{4}{9}=\frac{28}{63}\)

vì \(\frac{27}{63}< \frac{28}{63}\)

nên\(\frac{3}{7}< \frac{4}{9}\)

cau tren bai ghi de sai , con hai cau sau thi minh lam duoc  ;

-5/9<4/7

-1/2>-3/4

cái này k biết sao

a)\(\sqrt{9.4}=\sqrt{36}=6;\sqrt{9}.\sqrt{4}=3.2=6\Rightarrow\sqrt{9.4}=\sqrt{9}.\sqrt{4}\)

b)\(\sqrt{169-144}=\sqrt{25}=5;\sqrt{169}-\sqrt{144}=13-12=1\Rightarrow\sqrt{169-144}>\sqrt{169}-\sqrt{144}\)

tra loi ho mik lun di mai ik hoc roi !chut chut chuit chut

1: \(\left(\sqrt{3}+\sqrt{7}\right)^2=10+2\sqrt{21}\)

\(\left(2+\sqrt{6}\right)^2=10+4\sqrt{6}\)

mà 2 căn 21<4 căn 6

nên căn 3+căn 7<2+căn 6

2: \(\sqrt{7}-\sqrt{5}=\dfrac{2}{\sqrt{7}+\sqrt{5}}\)

\(\sqrt{6}-2=\dfrac{2}{\sqrt{6}+2}\)

mà \(\sqrt{7}+\sqrt{5}>\sqrt{6}+2\)

nên \(\sqrt{7}-\sqrt{5}< \sqrt{6}-2\)

3: \(\sqrt{11}-\sqrt{7}=\dfrac{4}{\sqrt{11}+\sqrt{7}}\)

\(\sqrt{7}-\sqrt{3}=\dfrac{4}{\sqrt{7}+\sqrt{3}}\)

mà căn 11>căn 3

nên \(\sqrt{11}-\sqrt{7}< \sqrt{7}-\sqrt{3}\)