関数は f(x) = x^2+x+1 です
**Upper Bound** when x>0, x^2 >= x^2 similarly, x >= x^2 and, 1 >= x^2
therefore, f(x)=x^2+x+1 >= x^2+x^2+x^2 (all sufficient large value of x)
>= 3x^2 , where c=3
f(x)= O(x^2)
**Lower Bound** f(x)=x^2+x+1 >= x^2 f(x) = Ω(x^2)
> しかし、下限を Ω(x) と Ω(1) と書くことはできますか?
f(x)=x^2+x+1 >= x (all sufficient large value of x) f(x) = Ω(x) ??
と
f(x)=x^2+x+1 >= 1 (all sufficient large value of x) f(x) = Ω(1) ?????