Biết rằng phương trình \(% MathType!MTEF!2!1!+- % feaahqart1ev3aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn % hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr % 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq-Jc9 % vqaqpepm0xbba9pwe9Q8fs0-yqaqpepae9pg0FirpepeKkFr0xfr-x % fr-xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGcbaGaciiBaiaac+ % gacaGGNbWaaSbaaSqaaiaaikdaaeqaaOGaamiEaiabgUcaRiGacYga % caGGVbGaai4zamaaBaaaleaacaaIZaaabeaakiaadIhacqGH9aqpca % aIXaGaey4kaSIaciiBaiaac+gacaGGNbWaaSbaaSqaaiaaikdaaeqa % aOGaamiEaiaac6caciGGSbGaai4BaiaacEgadaWgaaWcbaGaaG4maa % qabaGccaWG4baaaa!4D28! {\log _2}x + {\log _3}x = 1 + {\log _2}x.{\log _3}x\) có hai nghiệm \(x_1; x_2\). Giá trị của \(x_1^2+x_2^2\) là
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Lời giải:
Báo saiĐK:\(x>0\)
\(% MathType!MTEF!2!1!+- % feaahqart1ev3aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn % hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr % 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq-Jc9 % vqaqpepm0xbba9pwe9Q8fs0-yqaqpepae9pg0FirpepeKkFr0xfr-x % fr-xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGceaqabeaaciGGSb % Gaai4BaiaacEgadaWgaaWcbaGaaGOmaaqabaGccaWG4bGaey4kaSIa % ciiBaiaac+gacaGGNbWaaSbaaSqaaiaaiodaaeqaaOGaamiEaiabg2 % da9iaaigdacqGHRaWkciGGSbGaai4BaiaacEgadaWgaaWcbaGaaGOm % aaqabaGccaWG4bGaaiOlaiGacYgacaGGVbGaai4zamaaBaaaleaaca % aIZaaabeaakiaadIhaaeaacqGHuhY2ciGGSbGaai4BaiaacEgadaWg % aaWcbaGaaGOmaaqabaGccaWG4bGaeyOeI0IaaGymaiabg2da9iGacY % gacaGGVbGaai4zamaaBaaaleaacaaIZaaabeaakiaadIhacaGGUaGa % aiikaiGacYgacaGGVbGaai4zamaaBaaaleaacaaIYaaabeaakiaadI % hacqGHsislcaaIXaGaaiykaaqaaiabgsDiBlaacIcaciGGSbGaai4B % aiaacEgadaWgaaWcbaGaaGOmaaqabaGccaWG4bGaeyOeI0IaaGymai % aacMcacqGHsislciGGSbGaai4BaiaacEgadaWgaaWcbaGaaG4maaqa % baGccaWG4bGaaiOlaiaacIcaciGGSbGaai4BaiaacEgadaWgaaWcba % GaaGOmaaqabaGccaWG4bGaeyOeI0IaaGymaiaacMcacqGH9aqpcaaI % WaaabaGaeyi1HSTaaiikaiGacYgacaGGVbGaai4zamaaBaaaleaaca % aIYaaabeaakiaadIhacqGHsislcaaIXaGaaiykamaabmaabaGaaGym % aiabgkHiTiGacYgacaGGVbGaai4zamaaBaaaleaacaaIZaaabeaaki % aadIhaaiaawIcacaGLPaaacqGH9aqpcaaIWaaabaGaeyi1HS9aamqa % aqaabeqaaiGacYgacaGGVbGaai4zamaaBaaaleaacaaIYaaabeaaki % aadIhacqGHsislcaaIXaGaeyypa0JaaGimaaqaaiaaigdacqGHsisl % ciGGSbGaai4BaiaacEgadaWgaaWcbaGaaG4maaqabaGccaWG4bGaey % ypa0JaaGimaaaacaGLBbaaaeaacqGHuhY2daWabaabaeqabaGaciiB % aiaac+gacaGGNbWaaSbaaSqaaiaaikdaaeqaaOGaamiEaiabg2da9i % aaigdaaeaaciGGSbGaai4BaiaacEgadaWgaaWcbaGaaG4maaqabaGc % caWG4bGaeyypa0JaaGymaaaacaGLBbaaaeaacqGHuhY2daWabaabae % qabaGaamiEaiabg2da9iaaikdaaeaacaWG4bGaeyypa0JaaG4maaaa % caGLBbaaaaaa!BEE0! \begin{array}{l} {\log _2}x + {\log _3}x = 1 + {\log _2}x.{\log _3}x\\ \Leftrightarrow {\log _2}x - 1 = {\log _3}x.({\log _2}x - 1)\\ \Leftrightarrow ({\log _2}x - 1) - {\log _3}x.({\log _2}x - 1) = 0\\ \Leftrightarrow ({\log _2}x - 1)\left( {1 - {{\log }_3}x} \right) = 0\\ \Leftrightarrow \left[ \begin{array}{l} {\log _2}x - 1 = 0\\ 1 - {\log _3}x = 0 \end{array} \right.\\ \Leftrightarrow \left[ \begin{array}{l} {\log _2}x = 1\\ {\log _3}x = 1 \end{array} \right.\\ \Leftrightarrow \left[ \begin{array}{l} x = 2\\ x = 3 \end{array} \right. \end{array}\)
Vậy \(x_1^2+x_2^2=13\)
Đề thi thử tốt nghiệp THPT QG môn Toán năm 2020
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