=0 ⇒x=e Thus point x=e is the critical point for y=x1∕x Now at x=e,dy∕dx changes its sign from (+ve) to (−ve). Thus point (x=e) is point of global maxima. y=x3 has neither global minima nor global maxima, it only have saddle point at x=0 y|x|; attains its minimum value at x=0; so x=0 is the global minima for y=f(x)