السلام عليكم ورحمة الله تعالى وبركاته.
Let f :R--->R, C^2 (f" exist and is continous) such that
f(x) + f"(x) >= 0 for any x real
Show that, for any x we have f(x) + f(x+pi) >= 0
تحياتي للجميع.