Question

So sánh

a/ \(\dfrac{-2004}{-2005}\) và \(\dfrac{2005}{-2006}\)

b/\(\dfrac{5^{30}}{5^{20}}\) và 6\(^9\). (\(\dfrac{5}{6}\))\(^9\)

Answer 1

a/Ta có: \(\dfrac{-2004}{-2005}>0\) (*)
\(\dfrac{2005}{-2006}< 0\)(**)
Từ (*) và (**) \(\Rightarrow\)\(\dfrac{-2004}{-2005}>\dfrac{2005}{-2006}\)
b/ Ta có: \(\dfrac{5^{30}}{5^{20}}=5^{30}:5^{20}=5^{10}\)(*)
\(6^9.\left(\dfrac{5}{6}\right)^9=\left(\dfrac{6.5}{6}\right)^9=5^9\)(**)
Từ (*) và (**) suy ra: \(5^{10}>5^9\Rightarrow\dfrac{5^{30}}{5^{20}}>6^9.\left(\dfrac{5}{6}\right)^9\)

Answer 2

a, Ta có :

\(\dfrac{-2004}{-2005}>0\)\(\left(1\right)\)

\(\dfrac{2005}{-2005}< 0\left(2\right)\)

Từ \(\left(1\right)+\left(2\right)\Leftrightarrow\dfrac{-2004}{-2005}>\dfrac{2005}{-2006}\)