[Solved] If \(\int E^x (f(x) - F'(x))dx = \phi(x),\) Then T

Calculation:

Here, we have to find the value of the integrand \(\int e^x (f(x) - f'(x))dx = \phi(x)\)

\(\int e^xf'(x))dx =- \phi(x)+\int e^x f(x)dx\) --------------(1)

For given Integration \(\int e^x f(x)dx\) according to ILATE rule u = f(x); v = ex

\(\int {{e^x}} f(x)dx = f(x)\int {{e^x}dx} - \int {\left[ {\frac{{df(x)}}{{dx}}\int {{e^x}dx} } \right]} dx\)

\(\int {{e^x}} f(x)dx = f(x){e^x} - \int {f'(x){e^x}} dx\)

\(\int {{e^x}} f(x)dx = {e^x}f(x) - \int {{e^x}f'(x)} dx\)

Put the value of \(\int {{e^x}f'(x)} dx\) from equation (1)

\(\int {{e^x}} f(x)dx = {e^x}f(x) + \phi (x) - \int {{e^x}f(x)} dx\)

\(2\int {{e^x}} f(x)dx = {e^x}f(x) + \phi (x)\)

\(\int {{e^x}} f(x)dx = \frac{1}{2}[{e^x}f(x) + \phi (x)]\)

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