how to check quasiconcavity of such functions???

[Arushi :))]

1. f(x) = x if 0<,x<,1
          1 if 1<x<,2
          x-1 if x>2
2.f(x)= x^3+x^2+1 if , x <0
         1 if x>,= 0      

[Akshay Jain]

[ashutosh]

first function is both quasi concave. We can check that by drawing it on the xy plane. the upper level set f(x) =>a will be convex set.