Q$3[16$ pts$]$

Determine whether each of these functions is $O(x^2).$

To establish a big$-$O relationship, find witnesses $C$ and $k$ such that $|f(x)|C|g(x)|$ whenever $x>k.$

I. $f(x)=12x+10$

II$.f(x)=x^2+1500$

III. $,f(x)=xlogx$

IV$.f(x)={|}_{{?}_{?}}{x}_{{?}_{?}}|+|$~$x$~$||$