Multiple-choice questions BABDBCABCADB fill in the blanks -20 16 2/3 234 big questions 17. One small problem, two opposing problems, and two small problems -2. 18. One small problem 5/ 16 Two small problems 3.5 yuan. 19. One small problem is slightly two small problems 2/3 three small problems 1/3. 20 a small problem (hint: expand the n power of 1+x by binomial theorem, then take the derivative item by item, and multiply x around the equation) an = d (1+d) n The rest is very simple. Two small problems, first discussed, and then multiplied by the arithmetic. 2 1. One small problem k=+_2, and two small problems get 1. 22 A small problem is monotonic at 9/ 16, the minimum value is 1/8, two small problems are slight, and three small problems are greater than (suggesting that when n= 1, that formula gets 1/6, just make a difference to prove f (n) h (n