Question

hi everybody i have question on increasing and decreasing function
f(x)=x^1/2
it increasing on [0,&)
why 0 is including
and x^3-3x^2+1
it increasing on (-&,0].[2,&) why here also including since -x2 - 2x + 15 decreasing on
(-1, +∞) and 1 is not including