Re: Doubt

Posted by Asd1995 on Jun 15, 2017; 12:48pm
URL: http://discussion-forum.276.s1.nabble.com/Doubt-tp7605647p7605649.html

It means f'(x)*f(x)=0 for some x, which is true.

Consider f(x)<0 for all x. This implies the graph tapers off to some negative value as x approaches minus infinity. So derivative will tend to 0 there which will make product 0

Similarly consider f(X)>0 for all x. Graph tapers off at x=infinity, by the same argument the product vanishes to 0.

In other cases f(x)=0 for some x.