(1)计算:1/x−1/x+1=_,1/x+1−1/x+2=_,1/x+2−1/x+3=_; (2)计算:1/x(x+1)+1/(x+1)(x+2)+1/(x+2)(x+3)+…+1/(x+2013)(x+2014),当x=1时,求该代数式
问题描述:
(1)计算:
−1 x
=______,1 x+1
−1 x+1
=______,1 x+2
−1 x+2
=______;1 x+3
(2)计算:
+1 x(x+1)
+1 (x+1)(x+2)
+…+1 (x+2)(x+3)
,当x=1时,求该代数式的值. 1 (x+2013)(x+2014)
答
(1)
-1 x
=1 x+1
,1 x(x+1)
-1 x+1
=1 x+2
,1 (x+1)(x+2)
-1 x+2
=1 x+3
;1 (x+2)(x+3)
(2)原式=
-1 x
+1 x+1
-1 x+1
+…+1 x+2
-1 x+2013
=1 x+2014
-1 x
=1 x+2014
,2014 x(x+2014)
当x=1时,原式=
.2014 2015
故答案为:(1)
,1 x(x+1)
,1 (x+1)(x+2)
;1 (x+2)(x+3)