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I hope someone can help me with the following exercise... Show that $ \int_0^t s \, dB_s =tB_t-\int_0^t B_s \, ds $, for each $t>0$, where $B$ is a Brownian motion. Thanks in advance!!!

mari
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    This is direct from Itô's formula applied to $X_t=tB_t$. – Did Apr 29 '13 at 21:54
  • Since you now accepted a remarkably succinct answer, I hope you checked for yourself that Itô's formula did not introduce supplementary terms in the differentials involved. To wit, let me remind you that the "integration by parts" formula $X_sdB_s=d(X_sB_s)-B_sdX_s$ is not true for every process $(X_s)$... – Did May 02 '13 at 18:25

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I think you want to start with integration by parts:

$sdB_s=d(sB_s)-B_sds$