计算:1/3+1/6+1/10+1/15+1/21+1/28+1/36+1/45=_.
问题描述:
计算:
+1 3
+1 6
+1 10
+1 15
+1 21
+1 28
+1 36
=______. 1 45
答
+1 3
+1 6
+1 10
+1 15
+1 21
+1 28
+1 36
,1 45
=
+2 2×3
+2 3×4
+…+2 4×5
,2 9×10
=2[(
−1 2
)+(1 3
−1 3
)+(1 4
−1 4
)+…+(1 5
−1 9
)],1 10
=2(
−1 2
),1 10
=
;4 5
故答案为:
.4 5