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If $f$ is an $L^p$ function and $\int f(x)g(x)dx=0$ for every $L^p$ function $g$ does that imply that $f=0$ a.e

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    yes but if I am not mistaken what you are saying implies f=0 a.e2012-12-08

1 Answers 1

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Yes, it implies that $f=0$ a.e. For if we let $g=f$, then we have $\int f^2=0,$ and $f^2\geq0$. This implies that $f^2=0$ a.e., hence $f=0$ a.e.

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    oh I see. thank you very much both of you2012-12-08