Cho hàm số \(% MathType!MTEF!2!1!+- % feaahqart1ev3aqatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn % hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr % 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq-Jc9 % vqaqpepm0xbba9pwe9Q8fs0-yqaqpepae9pg0FirpepeKkFr0xfr-x % fr-xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGcbaGaamyEaiabg2 % da9iaadAgadaqadaqaaiaadIhaaiaawIcacaGLPaaacqGH9aqpdaWc % aaqaaiabgkHiTiaadIhadaahaaWcbeqaaiaaikdaaaGccqGHRaWkca % WG4bGaey4kaSIaaGOmaaqaaiaadIhacqGHsislcaaIXaaaaaaa!457E! y = f\left( x \right) = \frac{{ - {x^2} + x + 2}}{{x - 1}}\). Xét hai mệnh đề :
\(% MathType!MTEF!2!1!+- % feaahqart1ev3aqatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn % hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr % 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq-Jc9 % vqaqpepm0xbba9pwe9Q8fs0-yqaqpepae9pg0FirpepeKkFr0xfr-x % fr-xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGcbaWaaeWaaeaaca % WGjbaacaGLOaGaayzkaaGaaiOoaiqadMhagaqbaiabg2da9iqadAga % gaqbamaabmaabaGaamiEaaGaayjkaiaawMcaaaaa!3E96! \left( I \right):y' = f'\left( x \right)\) \(% MathType!MTEF!2!1!+- % feaahqart1ev3aqatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn % hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr % 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq-Jc9 % vqaqpepm0xbba9pwe9Q8fs0-yqaqpepae9pg0FirpepeKkFr0xfr-x % fr-xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGcbaGaeyypa0Jaey % OeI0IaaGymaiabgkHiTmaalaaabaGaaGOmaaqaaiaacIcacaWG4bGa % eyOeI0IaaGymaiaacMcadaahaaWcbeqaaiaaikdaaaaaaOGaeyipaW % JaaGimaiaacYcacqGHaiIicaWG4bGaeyiyIKRaaGymaaaa!4609! = - 1 - \frac{2}{{{{(x - 1)}^2}}} < 0,\forall x \ne 1\)
\(% MathType!MTEF!2!1!+- % feaahqart1ev3aqatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn % hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr % 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq-Jc9 % vqaqpepm0xbba9pwe9Q8fs0-yqaqpepae9pg0FirpepeKkFr0xfr-x % fr-xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGcbaWaaeWaaeaaca % WGjbGaamysaaGaayjkaiaawMcaaiaacQdaceWG5bGbayaacqGH9aqp % ceWGMbGbayaadaqadaqaaiaadIhaaiaawIcacaGLPaaaaaa!3F66! \left( {II} \right):y'' = f''\left( x \right)\) \(% MathType!MTEF!2!1!+- % feaahqart1ev3aqatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn % hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr % 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq-Jc9 % vqaqpepm0xbba9pwe9Q8fs0-yqaqpepae9pg0FirpepeKkFr0xfr-x % fr-xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGcbaGaeyypa0ZaaS % aaaeaacaaI0aaabaGaaiikaiaadIhacqGHsislcaaIXaGaaiykamaa % CaaaleqabaGaaGOmaaaaaaGccqGH+aGpcaaIWaGaaiilaiabgcGiIi % aadIhacqGHGjsUcaaIXaaaaa!437A! = \frac{4}{{{{(x - 1)}^2}}} > 0,\forall x \ne 1\)
Mệnh đề nào đúng
Hãy suy nghĩ và trả lời câu hỏi trước khi xem đáp án
Lời giải:
Báo saiy = f(x) = \(% MathType!MTEF!2!1!+- % feaahqart1ev3aqatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn % hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr % 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq-Jc9 % vqaqpepm0xbba9pwe9Q8fs0-yqaqpepae9pg0FirpepeKkFr0xfr-x % fr-xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGcbaGaeyypa0ZaaS % aaaeaacqGHsislcaWG4bWaaWbaaSqabeaacaaIYaaaaOGaey4kaSIa % amiEaiabgUcaRiaaikdaaeaacaWG4bGaeyOeI0IaaGymaaaaaaa!4009! = \frac{{ - {x^2} + x + 2}}{{x - 1}}\) \(% MathType!MTEF!2!1!+- % feaahqart1ev3aqatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn % hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr % 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq-Jc9 % vqaqpepm0xbba9pwe9Q8fs0-yqaqpepae9pg0FirpepeKkFr0xfr-x % fr-xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGcbaGaeyypa0Jaey % OeI0IaamiEaiabgUcaRmaalaaabaGaaGOmaaqaaiaadIhacqGHsisl % caaIXaaaaaaa!3D37! = - x + \frac{2}{{x - 1}}\) \(% MathType!MTEF!2!1!+- % feaahqart1ev3aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn % hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr % 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq-Jc9 % vqaqpepm0xbba9pwe9Q8fs0-yqaqpepae9pg0FirpepeKkFr0xfr-x % fr-xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGcbaGaeyO0H4Tabm % yEayaafaGaeyypa0JaeyOeI0IaaGymaiabgkHiTmaalaaabaGaaGOm % aaqaamaabmaabaGaamiEaiabgkHiTiaaigdaaiaawIcacaGLPaaada % ahaaWcbeqaaiaaikdaaaaaaaaa!42D8! \Rightarrow y' = - 1 - \frac{2}{{{{\left( {x - 1} \right)}^2}}}\)
\(% MathType!MTEF!2!1!+- % feaahqart1ev3aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn % hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr % 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq-Jc9 % vqaqpepm0xbba9pwe9Q8fs0-yqaqpepae9pg0FirpepeKkFr0xfr-x % fr-xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGcbaGabmyEayaaga % Gaeyypa0ZaaSaaaeaacaaI0aaabaWaaeWaaeaacaWG4bGaeyOeI0Ia % aGymaaGaayjkaiaawMcaamaaCaaaleqabaGaaG4maaaaaaaaaa!3DEA! y'' = \frac{4}{{{{\left( {x - 1} \right)}^3}}}\)
