2 (-4)(1)(3) (1)(2)(-3) (2) (3)(-5)
(5) -10 (5) (1) -10 (9) (1) -10 (9)
(-1)(9)(-8), (-2)(8)(-6) (-3)(7)(-4)
(1)原式=1-1/2+1/2-1/3+1/3-1/4...+1/2010-1/2011=1-1/2011=2010/2011
(2)原式=1-1/2+1/2-1/3+1/3-1/4...+1/2010-1/2011=1-1/2011=2010/2011
有不懂的可以继续问我
再问: 谢谢你>OO