Question Number 50411 by Abdo msup. last updated on 16/Dec/18
$${find}\:{all}\:{function}\:{f}\:\:{continues}\:{from}\:{R}\:{to}\:{R}\:/ \\ $$$$\forall\left({x},{h}\right)\in{R}^{\mathrm{2}} \:\:\:{f}\left({x}\right).{f}\left({y}\right)=\int_{{x}−{y}} ^{{x}+{y}} \:{f}\left({t}\right){dt}\:. \\ $$