Cho a,b là các số thực dương thỏa mãn \(% MathType!MTEF!2!1!+- % feaahqart1ev3aqaMTcvLHfij5gC1rhimfMBNvxyNvga7X1CXjhD7f % wFTW1CXjhD7jwFRetpW0hatCvAUfeBSjuyZL2yd9gzLbvyNv2Caerb % uLwBLnhiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharq % qtubsr4rNCHbGeaGqiVCI8FfYJH8YrFfeuY-Hhbbf9v8qqaqFr0xc9 % pk0xbba9q8WqFfeaY-biLkVcLq-JHqpepeea0-as0Fb9pgeaYRXxe9 % vr0-vr0-vqpWqaaeaabiGaciaacaqabeaadaqaaqaaaOqaaabaaaaa % aaaapeWaaOaaa8aabaWdbiaadggaaSqabaGccqGHsisldaGcaaWdae % aapeGaamOyaaWcbeaakiabgUcaRiaaigdacqGH9aqpcaaIWaaaaa!4CAB! \sqrt a - \sqrt b + 1 = 0\) . Tính tích phân \(% MathType!MTEF!2!1!+- % feaahqart1ev3aqaMDevLHfij5gC1rhimfMBNvxyNvga7LupCLMB0X % fBP1wA0n3x7fwFETNy9ThxMjxyJThx0vgE0Thz9HxF7X1CXjhD7HxF % 91xFamXvP5wqSXMqHnxAJn0BKvguHDwzZbqefqvATv2CG4uz3bIuV1 % wyUbqedmvETj2BSbqefm0B1jxALjhiov2DaebbnrfifHhDYfgasaac % H8YjY-vipgYlh9vqqj-hEeeu0xXdbba9frFj0-OqFfea0dXdd9vqai % -hGuQ8kuc9pgc9q8qqaq-dir-f0-yqaiVgFr0xfr-xfr-xb9adbaqa % aeGaciGaaiaabeqaamaabaabaaGcbaaeaaaaaaaaa8qacaWGjbGaey % ypa0Zaa8qCa8aabaWdbmaalaaapaqaa8qacaqGKbGaamiEaaWdaeaa % peWaaOaaa8aabaWdbiaadIhaaSqabaaaaaWdaeaapeGaamyyaaWdae % aapeGaamOyaaqdcqGHRiI8aaaa!5CEE! I = \int\limits_a^b {\frac{{{\rm{d}}x}}{{\sqrt x }}} \)
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Lời giải:
Báo saiTa có \(% MathType!MTEF!2!1!+- % feaahqart1ev3aqaMjovLHfij5gC1rhimfMBNvxyNvga7LupCLMB0X % fBP1wA0n3x7fwFETNy9ThxMjxyJThx0vgE0Thz9HxF7X1CXjhD7HxF % 91xpCLMB0XfBP1wA0n3x7fwFETNy9T3E7HxFETxlCzMCHn2EX03EY0 % xF9XfDLHhD7rwF41xpYW1CXjhD7HxFCXwzMrhFGWLyLDwAUTxBHrNC % PHxFnaciGigiGWfxnaciGegiGWfxnWvzUr2ETfgDYLgE91JmCXwzMr % hkGW1CXjhD7jwFTW1CXjhD7fwFGWLCPDgA0LciCjxANHgDU0hatCvA % UfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLnhiov2DGi1BTfMBaeXatL % xBI9gBaerbd9wDYLwzYbItLDharqqtubsr4rNCHbGeaGqiVCI8FfYJ % H8YrFfeuY-Hhbbf9v8qqaqFr0xc9pk0xbba9q8WqFfeaY-biLkVcLq % -JHqpepeea0-as0Fb9pgeaYRXxe9vr0-vr0-vqpWqaaeaabiGaciaa % caqabeaadaqaaqaaaOqaaabaaaaaaaaapeGaamysaiabg2da9maape % hapaqaa8qadaWcaaWdaeaapeGaaeizaiaadIhaa8aabaWdbmaakaaa % paqaa8qacaWG4baaleqaaaaaa8aabaWdbiaadggaa8aabaWdbiaadk % gaa0Gaey4kIipakiabg2da9maapehapaqaa8qacaWG4bWdamaaCaaa % leqabaWdbiabgkHiTmaalaaapaqaa8qacaaIXaaapaqaa8qacaaIYa % aaaaaakiaabsgacaWG4baal8aabaWdbiaadggaa8aabaWdbiaadkga % a0Gaey4kIipakiabg2da9iaaikdadaGcaaWdaeaapeGaamiEaaWcbe % aakmaaeeaapaqaauaabeqaceaaaeaapeGaamOyaaWdaeaapeGaamyy % aaaacqGH9aqpcaaIYaWaaeWaa8aabaWdbmaakaaapaqaa8qacaWGIb % aaleqaaOGaeyOeI0YaaOaaa8aabaWdbiaadggaaSqabaaakiaawIca % caGLPaaaaiaawEa7aaaa!B0A4! I = \int\limits_a^b {\frac{{{\rm{d}}x}}{{\sqrt x }}} = \int\limits_a^b {{x^{ - \frac{1}{2}}}{\rm{d}}x} = 2\sqrt x \left| {\begin{array}{*{20}{c}} b\\ a \end{array} = 2\left( {\sqrt b - \sqrt a } \right)} \right.(1)\)
Mà \(% MathType!MTEF!2!1!+- % feaahqart1ev3aqaMTcvLHfij5gC1rhimfMBNvxyNvga7X1CXjhD7f % wFTW1CXjhD7jwFRetpW0hatCvAUfeBSjuyZL2yd9gzLbvyNv2Caerb % uLwBLnhiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharq % qtubsr4rNCHbGeaGqiVCI8FfYJH8YrFfeuY-Hhbbf9v8qqaqFr0xc9 % pk0xbba9q8WqFfeaY-biLkVcLq-JHqpepeea0-as0Fb9pgeaYRXxe9 % vr0-vr0-vqpWqaaeaabiGaciaacaqabeaadaqaaqaaaOqaaabaaaaa % aaaapeWaaOaaa8aabaWdbiaadggaaSqabaGccqGHsisldaGcaaWdae % aapeGaamOyaaWcbeaakiabgUcaRiaaigdacqGH9aqpcaaIWaaaaa!4CAB! \sqrt a - \sqrt b + 1 = 0\)\(% MathType!MTEF!2!1!+- % feaahqart1ev3aqaMPcvLHfij5gC1rhimfMBNvxyNvga7X1CXjhD7f % wFTW1CXjhD7jwF90sm9bWexLMBbXgBcf2CPn2qVrwzqf2zLnharuav % P1wzZbItLDhis9wBH5garmWu51MyVXgaruWqVvNCPvMCG4uz3bqee0 % evGueE0jxyaibaieYlNi-xH8yiVC0xbbL8F4rqqrFfpeea0xe9Lq-J % c9vqaqpepm0xbbG8FasPYRqj0-yi0dXdbba9pGe9xq-JbbG8A8frFv % e9Fve9Ff0dmeaabaqaciGacaGaaeqabaWaaeaaeaaakeaaqaaaaaaa % aaWdbmaakaaapaqaa8qacaWGHbaaleqaaOGaeyOeI0YaaOaaa8aaba % WdbiaadkgaaSqabaGccqGH9aqpcqGHsislcaaIXaaaaa!4BCD! \iff\sqrt a - \sqrt b = - 1\)(2)
Từ (1) và (2) nên I = - 2