Cho hàm số f(x) có đạo hàm liên tục trên đoạn [0;1] và thỏa mãn f(0) = 6; \(% MathType!MTEF!2!1!+- % feaahqart1ev3aqatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn % hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr % 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq-Jc9 % vqaqpepm0xbba9pwe9Q8fs0-yqaqpepae9pg0FirpepeKkFr0xfr-x % fr-xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGcbaWaa8qCaeaada % qadaqaaiaaikdacaWG4bGaeyOeI0IaaGOmaaGaayjkaiaawMcaaiaa % c6caceWGMbGbauaadaqadaqaaiaadIhaaiaawIcacaGLPaaacaqGKb % GaamiEaiabg2da9iaaiAdaaSqaaiaaicdaaeaacaaIXaaaniabgUIi % Ydaaaa!4696! \int\limits_0^1 {\left( {2x - 2} \right).f'\left( x \right){\rm{d}}x = 6} \), . Tích phân \(% MathType!MTEF!2!1!+- % feaahqart1ev3aqatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn % hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr % 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq-Jc9 % vqaqpepm0xbba9pwe9Q8fs0-yqaqpepae9pg0FirpepeKkFr0xfr-x % fr-xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGcbaWaa8qmaeaaca % WGMbWaaeWaaeaacaWG4baacaGLOaGaayzkaaGaaeizaiaadIhaaSqa % aiaaicdaaeaacaaIXaaaniabgUIiYdaaaa!3EE7! \int_0^1 {f\left( x \right){\rm{d}}x} \)

Ta có \(% MathType!MTEF!2!1!+- % feaahqart1ev3aqatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn % hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr % 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq-Jc9 % vqaqpepm0xbba9pwe9Q8fs0-yqaqpepae9pg0FirpepeKkFr0xfr-x % fr-xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGcbaGaaGOnaiabg2 % da9maapehabaWaaeWaaeaacaaIYaGaamiEaiabgkHiTiaaikdaaiaa % wIcacaGLPaaacaGGUaGabmOzayaafaWaaeWaaeaacaWG4baacaGLOa % GaayzkaaGaaeizaiaadIhaaSqaaiaaicdaaeaacaaIXaaaniabgUIi % Ydaaaa!4696! 6 = \int\limits_0^1 {\left( {2x - 2} \right).f'\left( x \right){\rm{d}}x} \)\(% MathType!MTEF!2!1!+- % feaahqart1ev3aqatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn % hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr % 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq-Jc9 % vqaqpepm0xbba9pwe9Q8fs0-yqaqpepae9pg0FirpepeKkFr0xfr-x % fr-xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGcbaGaeyypa0Zaa8 % qCaeaadaqadaqaaiaaikdacaWG4bGaeyOeI0IaaGOmaaGaayjkaiaa % wMcaaiaabsgadaWadaqaaiaadAgadaqadaqaaiaadIhaaiaawIcaca % GLPaaaaiaawUfacaGLDbaaaSqaaiaaicdaaeaacaaIXaaaniabgUIi % Ydaaaa!460D! = \int\limits_0^1 {\left( {2x - 2} \right){\rm{d}}\left[ {f\left( x \right)} \right]} \) \(% MathType!MTEF!2!1!+- % feaahqart1ev3aqatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn % hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr % 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq-Jc9 % vqaqpepm0xbba9pwe9Q8fs0-yqaqpepae9pg0FirpepeKkFr0xfr-x % fr-xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGcbaGaeyypa0Zaaq % GaaeaadaWadaqaamaabmaabaGaaGOmaiaadIhacqGHsislcaaIYaaa % caGLOaGaayzkaaGaamOzamaabmaabaGaamiEaaGaayjkaiaawMcaaa % Gaay5waiaaw2faaaGaayjcSdWaa0baaSqaaiaaicdaaeaacaaIXaaa % aOGaeyOeI0IaaGOmamaapehabaGaamOzamaabmaabaGaamiEaaGaay % jkaiaawMcaaiaabsgacaWG4baaleaacaaIWaaabaGaaGymaaqdcqGH % RiI8aaaa!4F66! = \left. {\left[ {\left( {2x - 2} \right)f\left( x \right)} \right]} \right|_0^1 - 2\int\limits_0^1 {f\left( x \right){\rm{d}}x} \)

\(% MathType!MTEF!2!1!+- % feaahqart1ev3aqatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn % hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr % 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq-Jc9 % vqaqpepm0xbba9pwe9Q8fs0-yqaqpepae9pg0FirpepeKkFr0xfr-x % fr-xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGcbaGaeyi1HSTaaG % Onaiabg2da9iabgkHiTiaaikdacaWGMbWaaeWaaeaacaaIWaaacaGL % OaGaayzkaaGaeyOeI0IaaGOmamaapehabaGaamOzamaabmaabaGaam % iEaaGaayjkaiaawMcaaiaabsgacaWG4baaleaacaaIWaaabaGaaGym % aaqdcqGHRiI8aaaa!49C9! \Leftrightarrow 6 = - 2f\left( 0 \right) - 2\int\limits_0^1 {f\left( x \right){\rm{d}}x} \) \(% MathType!MTEF!2!1!+- % feaahqart1ev3aqatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn % hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr % 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq-Jc9 % vqaqpepm0xbba9pwe9Q8fs0-yqaqpepae9pg0FirpepeKkFr0xfr-x % fr-xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGcbaWaa8qCaeaaca % WGMbWaaeWaaeaacaWG4baacaGLOaGaayzkaaGaaeizaiaadIhaaSqa % aiaaicdaaeaacaaIXaaaniabgUIiYdGccqGH9aqpaaa!4037! \iff\int\limits_0^1 {f\left( x \right){\rm{d}}x} = \)\(% MathType!MTEF!2!1!+- % feaahqart1ev3aqatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn % hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr % 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq-Jc9 % vqaqpepm0xbba9pwe9Q8fs0-yqaqpepae9pg0FirpepeKkFr0xfr-x % fr-xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGcbaWaaSaaaeaacq % GHsislcaaIYaGaamOzamaabmaabaGaaGimaaGaayjkaiaawMcaaiab % gkHiTiaaiAdaaeaacaaIYaaaaaaa!3D44! \frac{{ - 2f\left( 0 \right) - 6}}{2} = -9\)