Cho bất phương trình \(% MathType!MTEF!2!1!+- % feaahqart1ev3aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn % hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr % 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq-Jc9 % vqaqpepm0xbba9pwe9Q8fs0-yqaqpepae9pg0FirpepeKkFr0xfr-x % fr-xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGcbaWaaSaaaeaaca % aIXaGaeyOeI0IaciiBaiaac+gacaGGNbWaaSbaaSqaaiaaiMdaaeqa % aOGaamiEaaqaaiaaigdacqGHRaWkciGGSbGaai4BaiaacEgadaWgaa % WcbaGaaG4maaqabaGccaWG4baaaiabgsMiJoaalaaabaGaaGymaaqa % aiaaikdaaaaaaa!460A! \frac{{1 - {{\log }_9}x}}{{1 + {{\log }_3}x}} \le \frac{1}{2}\). Nếu đặt \(% MathType!MTEF!2!1!+- % feaahqart1ev3aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn % hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr % 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq-Jc9 % vqaqpepm0xbba9pwe9Q8fs0-yqaqpepae9pg0FirpepeKkFr0xfr-x % fr-xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGcbaGaamiDaiabg2 % da9iGacYgacaGGVbGaai4zamaaBaaaleaacaaIZaaabeaakiaadIha % aaa!3CB2! t = {\log _3}x\) thì bất phương
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Lời giải:
Báo sai\(% MathType!MTEF!2!1!+- % feaahqart1ev3aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn % hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr % 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq-Jc9 % vqaqpepm0xbba9pwe9Q8fs0-yqaqpepae9pg0FirpepeKkFr0xfr-x % fr-xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGcbiqaam4rdaWcaa % qaaiaaigdacqGHsislciGGSbGaai4BaiaacEgadaWgaaWcbaGaaGyo % aaqabaGccaWG4baabaGaaGymaiabgUcaRiGacYgacaGGVbGaai4zam % aaBaaaleaacaaIZaaabeaakiaadIhaaaGaeyizIm6aaSaaaeaacaaI % XaaabaGaaGOmaaaacqGHuhY2daWcaaqaaiaaigdacqGHsisldaWcaa % qaaiaaigdaaeaacaaIYaaaaiGacYgacaGGVbGaai4zamaaBaaaleaa % caaIZaaabeaakiaadIhaaeaacaaIXaGaey4kaSIaciiBaiaac+gaca % GGNbWaaSbaaSqaaiaaiodaaeqaaOGaamiEaaaacqGHKjYOdaWcaaqa % aiaaigdaaeaacaaIYaaaaiabgsDiBpaalaaabaGaaGOmaiabgkHiTi % GacYgacaGGVbGaai4zamaaBaaaleaacaaIZaaabeaakiaadIhaaeaa % caaIYaWaaeWaaeaacaaIXaGaey4kaSIaciiBaiaac+gacaGGNbWaaS % baaSqaaiaaiodaaeqaaOGaamiEaaGaayjkaiaawMcaaaaacqGHKjYO % daWcaaqaaiaaigdaaeaacaaIYaaaaiabgsDiBlaaigdacqGHsislda % WcaaqaaiaaikdacqGHsislciGGSbGaai4BaiaacEgadaWgaaWcbaGa % aG4maaqabaGccaWG4baabaGaaGymaiabgUcaRiGacYgacaGGVbGaai % 4zamaaBaaaleaacaaIZaaabeaakiaadIhaaaGaeyyzImRaaGimaiab % gsDiBpaalaaabaGaaGOmaiGacYgacaGGVbGaai4zamaaBaaaleaaca % aIZaaabeaakiaadIhacqGHsislcaaIXaaabaGaaGymaiabgUcaRiGa % cYgacaGGVbGaai4zamaaBaaaleaacaaIZaaabeaakiaadIhaaaGaey % yzImRaaGimaaaa!9545! \frac{{1 - {{\log }_9}x}}{{1 + {{\log }_3}x}} \le \frac{1}{2} \Leftrightarrow \frac{{1 - \frac{1}{2}{{\log }_3}x}}{{1 + {{\log }_3}x}} \le \frac{1}{2} \Leftrightarrow \frac{{2 - {{\log }_3}x}}{{2\left( {1 + {{\log }_3}x} \right)}} \le \frac{1}{2} \Leftrightarrow 1 - \frac{{2 - {{\log }_3}x}}{{1 + {{\log }_3}x}} \ge 0 \Leftrightarrow \frac{{2{{\log }_3}x - 1}}{{1 + {{\log }_3}x}} \ge 0\)