Hàm số \(f(x)=x^3-3x^2+2\) đồng biến trên khoảng nào dưới đây
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Lời giải:
Báo sai\(% MathType!MTEF!2!1!+- % feaahqart1ev3aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn % hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr % 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq-Jc9 % vqaqpepm0xbba9pwe9Q8fs0-yqaqpepae9pg0FirpepeKkFr0xfr-x % fr-xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGceaqabeaacaWGMb % GaaiikaiaadIhacaGGPaGaeyypa0JaamiEamaaCaaaleqabaGaaG4m % aaaakiabgkHiTiaaiodacaWG4bWaaWbaaSqabeaacaaIYaaaaOGaey % 4kaSIaaGOmaiabgkDiElaadAgacaGGNaGaaiikaiaadIhacaGGPaGa % eyypa0JaaG4maiaadIhadaahaaWcbeqaaiaaikdaaaGccqGHsislca % aI2aGaamiEaaqaaiaadAgacaGGNaGaaiikaiaadIhacaGGPaGaeyyp % a0JaaGimaiabgsDiBlaaiodacaWG4bWaaWbaaSqabeaacaaIYaaaaO % GaeyOeI0IaaGOnaiaadIhacqGH9aqpcaaIWaGaeyi1HS9aamqaaqaa % beqaaiaadIhacqGH9aqpcaaIWaaabaGaamiEaiabg2da9iaaigdaae % aacaWG4bGaeyypa0JaeyOeI0IaaGymaaaacaGLBbaaaaaa!69B4! \begin{array}{l} f(x) = {x^3} - 3{x^2} + 2 \Rightarrow f'(x) = 3{x^2} - 6x\\ f'(x) = 0 \Leftrightarrow 3{x^2} - 6x = 0 \Leftrightarrow \left[ \begin{array}{l} x = 0\\ x = 2 \end{array} \right. \end{array}\)
Để hàm số đồng biến thì \(% MathType!MTEF!2!1!+- % feaahqart1ev3aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn % hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr % 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq-Jc9 % vqaqpepm0xbba9pwe9Q8fs0-yqaqpepae9pg0FirpepeKkFr0xfr-x % fr-xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGcbaGaamOzaiaacE % cacaGGOaGaamiEaiaacMcacqGH+aGpcaaIWaGaeyi1HS9aamqaaqaa % beqaaiaadIhacqGH8aapcaaIWaaabaGaamiEaiabg6da+iaaikdaaa % Gaay5waaaaaa!447B! f'(x) > 0 \Leftrightarrow \left[ \begin{array}{l} x < 0\\ x > 2 \end{array} \right.\)
Vậy hàm số đồng biến trên \(% MathType!MTEF!2!1!+- % feaahqart1ev3aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn % hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr % 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq-Jc9 % vqaqpepm0xbba9pwe9Q8fs0-yqaqpepae9pg0FirpepeKkFr0xfr-x % fr-xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGcbaGaaiikaiabgk % HiTiabg6HiLkaacUdacaaIWaGaaiykaiabgQIiilaacIcacaaIYaGa % ai4oaiabgUcaRiabg6HiLkaacMcaaaa!41EA! ( - \infty ;0) \cup (2; + \infty )\)
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