So sánh \(C = \frac{{{{98}^{99}} + 1}}{{{{98}^{89}} + 1}}\) và \(D = \frac{{{{98}^{98}} + 1}}{{{{98}^{88}} + 1}}\)
\(\begin{array}{l}
C = \frac{{{{98}^{99}} + 1}}{{{{98}^{89}} + 1}} > 1\\
\Rightarrow C = \frac{{{{98}^{99}} + 1}}{{{{98}^{89}} + 1}} > \frac{{{{98}^{99}} + 1 + 97}}{{{{98}^{89}} + 1 + 97}}\\
= \frac{{{{98}^{99}} + 98}}{{{{98}^{89}} + 98}} = \frac{{98\left( {{{98}^{98}} + 1} \right)}}{{98\left( {{{98}^{88}} + 1} \right)}}\\
= \frac{{{{98}^{98}} + 1}}{{{{98}^{88}} + 1}} = D
\end{array}\)
-- Mod Toán 6
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