To establish a big-O relationship, find witnesses C and k such that |f(x)| < C|g(x)|whenever x> k. Determine whether each of the following functions is 0(x). a) f(x) = 10

b) f(x) = 3x+ 7 c) f(x) =x² +x+1 d) f(x) = 5 log x e) f(x) = [x/2]