time complexity – Why do these functions satisfy that f(n) is not O(g(n)) and g(n) is not O(f(n))?

I don’t understand what these function are like and why they satisfy that f(n) is not O(g(n)) and g(n) is not O(f(n)).

Where is x?

begin{eqnarray}
f(x)=
begin{cases}
k^{2k}, &xin(2π‘˜,2π‘˜+1)& \
k^{2k+1}, &xin(2π‘˜+1,2π‘˜+2)&
end{cases}
end{eqnarray}

begin{eqnarray}
g(x)=
begin{cases}
k^{2k-2}, &xin(2π‘˜,2π‘˜+1)& \
k^{2k+2}, &xin(2π‘˜+1,2π‘˜+2)&
end{cases}
end{eqnarray}

Also, could you teach me how to write these functions in Grapher on MacOS? Cuz I want to know what they are like.