Cho a là số thực thỏa mãn |a| < 2 và \(% MathType!MTEF!2!1!+- % feaahqart1ev3aqatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn % hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr % 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq-Jc9 % vqaqpepm0xbba9pwe9Q8fs0-yqaqpepae9pg0FirpepeKkFr0xfr-x % fr-xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGcbaWaa8qCaeaada % qadaqaaiaaikdacaWG4bGaey4kaSIaaGymaaGaayjkaiaawMcaaiaa % bsgacaWG4baaleaacaWGHbaabaGaaGOmaaqdcqGHRiI8aOGaeyypa0 % JaaGinaaaa!4290! \int\limits_a^2 {\left( {2x + 1} \right){\rm{d}}x} = 4\). Giá trị biểu thức \(% MathType!MTEF!2!1!+- % feaahqart1ev3aqatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn % hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr % 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq-Jc9 % vqaqpepm0xbba9pwe9Q8fs0-yqaqpepae9pg0FirpepeKkFr0xfr-x % fr-xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGcbaGaaGymaiabgU % caRiaadggadaahaaWcbeqaaiaaiodaaaaaaa!3961! 1 + {a^3}\) bằng.
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Lời giải:
Báo saiTa có \(% MathType!MTEF!2!1!+- % feaahqart1ev3aqatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn % hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr % 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq-Jc9 % vqaqpepm0xbba9pwe9Q8fs0-yqaqpepae9pg0FirpepeKkFr0xfr-x % fr-xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGcbaWaa8qCaeaada % qadaqaaiaaikdacaWG4bGaey4kaSIaaGymaaGaayjkaiaawMcaaiaa % bsgacaWG4baaleaacaWGHbaabaGaaGOmaaqdcqGHRiI8aaaa!40C2! \int\limits_a^2 {\left( {2x + 1} \right){\rm{d}}x} \)\(% MathType!MTEF!2!1!+- % feaahqart1ev3aqatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn % hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr % 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq-Jc9 % vqaqpepm0xbba9pwe9Q8fs0-yqaqpepae9pg0FirpepeKkFr0xfr-x % fr-xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGcbaGaeyypa0Zaaq % GaaeaadaqadaqaaiaadIhadaahaaWcbeqaaiaaikdaaaGccqGHRaWk % caWG4baacaGLOaGaayzkaaaacaGLiWoadaqhaaWcbaGaamyyaaqaai % aaikdaaaGccqGH9aqpcaaI2aGaeyOeI0IaamyyamaaCaaaleqabaGa % aGOmaaaakiabgkHiTiaadggaaaa!4620! = \left. {\left( {{x^2} + x} \right)} \right|_a^2 = 6 - {a^2} - a\)
Theo đề \(% MathType!MTEF!2!1!+- % feaahqart1ev3aqatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn % hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr % 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq-Jc9 % vqaqpepm0xbba9pwe9Q8fs0-yqaqpepae9pg0FirpepeKkFr0xfr-x % fr-xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGcbaWaaiqaaqaabe % qaamaaemaabaGaamyyaaGaay5bSlaawIa7aiabgYda8iaaikdaaeaa % caaI2aGaeyOeI0IaamyyamaaCaaaleqabaGaaGOmaaaakiabgkHiTi % aadggacqGH9aqpcaaI0aaaaiaawUhaaiabgkDiElaadggacqGH9aqp % caaIXaaaaa!48FE! \left\{ \begin{array}{l} \left| a \right| < 2\\ 6 - {a^2} - a = 4 \end{array} \right. \Rightarrow a = 1\)
Vậy \(% MathType!MTEF!2!1!+- % feaahqart1ev3aqatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn % hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr % 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq-Jc9 % vqaqpepm0xbba9pwe9Q8fs0-yqaqpepae9pg0FirpepeKkFr0xfr-x % fr-xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGcbaGaaGymaiabgU % caRiaadggadaahaaWcbeqaaiaaiodaaaGccqGH9aqpcaaIYaaaaa!3B2D! 1 + {a^3} = 2\)