Số các giá trị nguyên của tham số m để phương trình \(% MathType!MTEF!2!1!+- % feaahqart1ev3aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn % hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr % 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq-Jc9 % vqaqpepm0xbba9pwe9Q8fs0-yqaqpepae9pg0FirpepeKkFr0xfr-x % fr-xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGcbaGaciiBaiaac+ % gacaGGNbWaaSbaaSqaamaakaaabaGaaGOmaaadbeaaaSqabaGcdaqa % daqaaiaadIhacqGHsislcaaIXaaacaGLOaGaayzkaaGaeyypa0Jaci % iBaiaac+gacaGGNbWaaSbaaSqaaiaaikdaaeqaaOWaaeWaaeaacaWG % TbGaamiEaiabgkHiTiaaiIdaaiaawIcacaGLPaaaaaa!47F9! {\log _{\sqrt 2 }}\left( {x - 1} \right) = {\log _2}\left( {mx - 8} \right)\) có hai nghiệm phân biệt là
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Lời giải:
Báo sai\(% MathType!MTEF!2!1!+- % feaahqart1ev3aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn % hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr % 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq-Jc9 % vqaqpepm0xbba9pwe9Q8fs0-yqaqpepae9pg0FirpepeKkFr0xfr-x % fr-xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGcbaGaciiBaiaac+ % gacaGGNbWaaSbaaSqaamaakaaabaGaaGOmaaadbeaaaSqabaGcdaqa % daqaaiaadIhacqGHsislcaaIXaaacaGLOaGaayzkaaGaeyypa0Jaci % iBaiaac+gacaGGNbWaaSbaaSqaaiaaikdaaeqaaOWaaeWaaeaacaWG % TbGaamiEaiabgkHiTiaaiIdaaiaawIcacaGLPaaacqGHuhY2caaMc8 % UaaGPaVpaaceaaeaqabeaacaWG4bGaeyOpa4JaaGymaaqaamaabmaa % baGaamiEaiabgkHiTiaaigdaaiaawIcacaGLPaaadaahaaWcbeqaai % aaikdaaaGccqGH9aqpcaWGTbGaamiEaiabgkHiTiaaiIdaaaGaay5E % aaGaaGPaVlaaykW7cqGHuhY2caaMc8UaaGPaVpaaceaaeaqabeaaca % WG4bGaeyOpa4JaaGymaaqaaiaadIhadaahaaWcbeqaaiaaikdaaaGc % cqGHsisldaqadaqaaiaad2gacqGHRaWkcaaIYaaacaGLOaGaayzkaa % GaamiEaiabgUcaRiaaiMdacqGH9aqpcaaIWaaaaiaawUhaaiaaykW7 % caaMc8oaaa!75E8! {\log _{\sqrt 2 }}\left( {x - 1} \right) = {\log _2}\left( {mx - 8} \right) \Leftrightarrow \,\,\left\{ \begin{array}{l} x > 1\\ {\left( {x - 1} \right)^2} = mx - 8 \end{array} \right.\,\, \Leftrightarrow \,\,\left\{ \begin{array}{l} x > 1\\ {x^2} - \left( {m + 2} \right)x + 9 = 0 \end{array} \right.\,\,\)
Để phương trình đã cho có hai nghiệm thực lớn hơn 1 thì điều kiện sau thỏa mãn.
\(% MathType!MTEF!2!1!+- % feaahqart1ev3aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn % hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr % 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq-Jc9 % vqaqpepm0xbba9pwe9Q8fs0-yqaqpepae9pg0FirpepeKkFr0xfr-x % fr-xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGcbaGaaGPaVlaayk % W7daGabaabaeqabaGaeuiLdqKaeyOpa4JaaGimaaqaaiaaigdacqGH % 8aapcaWG4bWaaSbaaSqaaiaaigdaaeqaaOGaeyipaWJaamiEamaaBa % aaleaacaaIYaaabeaaaaGccaGL7baacaaMc8UaaGPaVlabgsDiBlaa % ykW7daGabaabaeqabaGaamyBamaaCaaaleqabaGaaGOmaaaakiabgU % caRiaaisdacaWGTbGaeyOeI0IaaG4maiaaikdacqGH+aGpcaaIWaaa % baWaaeWaaeaacaWG4bWaaSbaaSqaaiaaigdaaeqaaOGaeyOeI0IaaG % ymaaGaayjkaiaawMcaaiabgUcaRmaabmaabaGaamiEamaaBaaaleaa % caaIYaaabeaakiabgkHiTiaaigdaaiaawIcacaGLPaaacqGH+aGpca % aIWaaabaWaaeWaaeaacaWG4bWaaSbaaSqaaiaaigdaaeqaaOGaeyOe % I0IaaGymaaGaayjkaiaawMcaamaabmaabaGaamiEamaaBaaaleaaca % aIYaaabeaakiabgkHiTiaaigdaaiaawIcacaGLPaaacqGH+aGpcaaI % WaaaaiaawUhaaiaaykW7caaMc8Uaeyi1HS9aaiqaaqaabeqaamaade % aaeaqabeaacaWGTbGaeyipaWJaeyOeI0IaaGioaaqaaiaad2gacqGH % +aGpcaaI0aaaaiaawUfaaaqaaiaad2gacqGH+aGpcaaIWaaabaGaaG % ioaiabgkHiTiaad2gacqGH+aGpcaaIWaaaaiaawUhaaiaaykW7caaM % c8Uaeyi1HSTaaGinaiabgYda8iaad2gacqGH8aapcaaI4aaaaa!8C8A! \,\,\left\{ \begin{array}{l} \Delta > 0\\ 1 < {x_1} < {x_2} \end{array} \right.\,\, \Leftrightarrow \,\left\{ \begin{array}{l} {m^2} + 4m - 32 > 0\\ \left( {{x_1} - 1} \right) + \left( {{x_2} - 1} \right) > 0\\ \left( {{x_1} - 1} \right)\left( {{x_2} - 1} \right) > 0 \end{array} \right.\,\, \Leftrightarrow \left\{ \begin{array}{l} \left[ \begin{array}{l} m < - 8\\ m > 4 \end{array} \right.\\ m > 0\\ 8 - m > 0 \end{array} \right.\,\, \Leftrightarrow 4 < m < 8\)
Vì \(% MathType!MTEF!2!1!+- % feaahqart1ev3aqatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn % hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr % 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq-Jc9 % vqaqpepm0xbba9pwe9Q8fs0-yqaqpepae9pg0FirpepeKkFr0xfr-x % fr-xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGcbaGaamyBaiabgI % GiolablssiIkabgkDiElaad2gacqGHiiIZdaGadaqaaiaaiwdacaGG % SaGaaGOnaiaacYcacaaI3aaacaGL7bGaayzFaaaaaa!4486! m \in Z\Rightarrow m \in \left\{ {5,6,7} \right\}\)
Đề thi thử tốt nghiệp THPT QG môn Toán năm 2020
Tuyển chọn số 1