Cho hàm số \(% MathType!MTEF!2!1!+- % feaahqart1ev3aqatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn % hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr % 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq-Jc9 % vqaqpepm0xbba9pwe9Q8fs0-yqaqpepae9pg0FirpepeKkFr0xfr-x % fr-xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGcbaGaamyEaiabg2 % da9iGacogacaGGVbGaai4CamaabmaabaWaaSaaaeaacaaIYaGaeqiW % dahabaGaaG4maaaacqGHRaWkcaaIYaGaamiEaaGaayjkaiaawMcaaa % aa!4235! y = \cos \left( {\frac{{2\pi }}{3} + 2x} \right)\). Khi đó phương trình y'=0 có nghiệm là:
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Lời giải:
Báo sai\(% MathType!MTEF!2!1!+- % feaahqart1ev3aqatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn % hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr % 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq-Jc9 % vqaqpepm0xbba9pwe9Q8fs0-yqaqpepae9pg0FirpepeKkFr0xfr-x % fr-xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGcbaGabmyEayaafa % Gaeyypa0JaeyOeI0IaaGOmaiaac6caciGGZbGaaiyAaiaac6gadaqa % daqaamaalaaabaGaaGOmaiabec8aWbqaaiaaiodaaaGaey4kaSIaaG % OmaiaadIhaaiaawIcacaGLPaaaaaa!44A1! y' = - 2.\sin \left( {\frac{{2\pi }}{3} + 2x} \right)\)
theo giả thiết \(% MathType!MTEF!2!1!+- % feaahqart1ev3aqatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn % hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr % 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq-Jc9 % vqaqpepm0xbba9pwe9Q8fs0-yqaqpepae9pg0FirpepeKkFr0xfr-x % fr-xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGcbaGabmyEayaafa % Gaeyypa0JaaGimaiabgsDiBlGacohacaGGPbGaaiOBamaabmaabaWa % aSaaaeaacaaIYaGaeqiWdahabaGaaG4maaaacqGHRaWkcaaIYaGaam % iEaaGaayjkaiaawMcaaiabg2da9iaaicdaaaa!471C! y' = 0 \Leftrightarrow \sin \left( {\frac{{2\pi }}{3} + 2x} \right) = 0\) \(% MathType!MTEF!2!1!+- % feaahqart1ev3aqatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn % hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr % 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq-Jc9 % vqaqpepm0xbba9pwe9Q8fs0-yqaqpepae9pg0FirpepeKkFr0xfr-x % fr-xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGcbaGaeyi1HSTaam % iEaiabg2da9iabgkHiTmaalaaabaGaeqiWdahabaGaaG4maaaacqGH % RaWkdaWcaaqaaiaadUgacqaHapaCaeaacaaIYaaaaiaabccacaqGGa % GaaeiiaiaabccacaqGGaGaaeiiaiaabccadaqadaqaaiaadUgacqGH % iiIZcqWIKeIOaiaawIcacaGLPaaaaaa!4C0F! \Leftrightarrow x = - \frac{\pi }{3} + \frac{{k\pi }}{2}{\rm{ }}\left( {k \in Z} \right)\)