Trong các hàm số sau, hàm số nào là hàm số chẵn?
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Lời giải:
Báo saiChọn B.
TXĐ: \(D=\mathbb{R}\)
\(% MathType!MTEF!2!1!+- % feaahqart1ev3aaatCvAUfKttLearuGlw5gvP1wzaeXatLxBI9gBam % XvP5wqSXMqHnxAJn0BKvguHDwzZbqegm0B1jxALjhiov2DaeHbuLwB % Lnhiov2DGi1BTfMBaebbnrfifHhDYfgasaacH8srps0lbbf9q8WrFf % euY-Hhbbf9v8qqaqFr0xc9pk0xbba9q8WqFfea0-yr0RYxir-Jbba9 % q8aq0-yq-He9q8qqQ8frFve9Fve9Ff0dmeaabaqaciGacaGaaeqaba % WaaqaafaaakeaacqGHaiIicqWG4baEcqGHiiIZcqWGebarcqGHshI3 % cqGHsislcqWG4baEcqGHiiIZcqWGebaraaa!4732! \forall x \in D \Rightarrow - x \in D\)
\(% MathType!MTEF!2!1!+- % feaahqart1ev3aaatCvAUfKttLearuGlw5gvP1wzaeXatLxBI9gBam % XvP5wqSXMqHnxAJn0BKvguHDwzZbqegm0B1jxALjhiov2DaeHbuLwB % Lnhiov2DGi1BTfMBaebbnrfifHhDYfgasaacH8srps0lbbf9q8WrFf % euY-Hhbbf9v8qqaqFr0xc9pk0xbba9q8WqFfea0-yr0RYxir-Jbba9 % q8aq0-yq-He9q8qqQ8frFve9Fve9Ff0dmeaabaqaciGacaGaaeqaba % WaaqaafaaakqaabeqaaiabdAgaMnaabmaabaGaeyOeI0IaemiEaGha % caGLOaGaayzkaaGaeyypa0ZaaqWaaeaacqaIYaGmcqGGUaGldaqada % qaaiabgkHiTiabdIha4bGaayjkaiaawMcaaiabgUcaRiabigdaXaGa % ay5bSlaawIa7aiabgUcaRmaaemaabaGaeGymaeJaeyOeI0IaeGOmai % ZaaeWaaeaacqGHsislcqWG4baEaiaawIcacaGLPaaaaiaawEa7caGL % iWoaaeaacaaMc8UaaGPaVlaaykW7caaMc8UaaGPaVlaaykW7caaMc8 % UaaGPaVlaaykW7caaMc8UaaGPaVlaaykW7caaMc8UaaGPaVlaaykW7 % cqGH9aqpdaabdaqaaiabgkHiTiabikdaYiabdIha4jabgUcaRiabig % daXaGaay5bSlaawIa7aiabgUcaRmaaemaabaGaeGymaeJaey4kaSIa % eGOmaiJaemiEaGhacaGLhWUaayjcSdaabaGaaGPaVlaaykW7caaMc8 % UaaGPaVlaaykW7caaMc8UaaGPaVlaaykW7caaMc8UaaGPaVlaaykW7 % caaMc8UaaGPaVlaaykW7caaMc8Uaeyypa0ZaaqWaaeaacqaIXaqmcq % GHsislcqaIYaGmcqWG4baEaiaawEa7caGLiWoacqGHRaWkdaabdaqa % aiabikdaYiabdIha4jabgUcaRiabigdaXaGaay5bSlaawIa7aaqaai % aaykW7caaMc8UaaGPaVlaaykW7caaMc8UaaGPaVlaaykW7caaMc8Ua % aGPaVlaaykW7caaMc8UaaGPaVlaaykW7caaMc8UaaGPaVlabg2da9m % aaemaabaGaeGOmaiJaemiEaGNaey4kaSIaeGymaedacaGLhWUaayjc % SdGaey4kaSYaaqWaaeaacqaIXaqmcqGHsislcqaIYaGmcqWG4baEai % aawEa7caGLiWoaaeaacaaMc8UaaGPaVlaaykW7caaMc8UaaGPaVlaa % ykW7caaMc8UaaGPaVlaaykW7caaMc8UaaGPaVlaaykW7caaMc8UaaG % PaVlaaykW7cqGH9aqpcqWGMbGzdaqadaqaaiabdIha4bGaayjkaiaa % wMcaaaaaaa!EBB1! \begin{array}{l} f\left( { - x} \right) = \left| {2.\left( { - x} \right) + 1} \right| + \left| {1 - 2\left( { - x} \right)} \right|\\ \,\,\,\,\,\,\,\,\,\,\,\,\,\,\, = \left| { - 2x + 1} \right| + \left| {1 + 2x} \right|\\ \,\,\,\,\,\,\,\,\,\,\,\,\,\,\, = \left| {1 - 2x} \right| + \left| {2x + 1} \right|\\ \,\,\,\,\,\,\,\,\,\,\,\,\,\,\, = \left| {2x + 1} \right| + \left| {1 - 2x} \right|\\ \,\,\,\,\,\,\,\,\,\,\,\,\,\,\, = f\left( x \right) \end{array}\)
Vậy hàm số là hàm số chẵn.