a = 1/2 * 3/4 * 5/6 *…… * 2007/2008b = 2/3 * 4/5 * 6/7 *…… * 2008/2009a、b 都是 1004 项的乘积,且 b/2 < a < b1.a * a < a*b = 1 / 2009 < (1/40) ² => a < 1/40 2.a * a > a*b /2 = 1/ 5018 > (1/80)...