In Exercises 1-14, to establish a big-O relationship, find wit- nesses C and k such that |f (x)l 3 Clg(x)| whenever > k. 1. Determine whether each of these functions is O(x). a) f(x)=10 c)/(x)=x2+x+1 e) f(x)=Lx b) f(x) = 3x + 7 d)/(x)= 5 log x f) f(x)= 21