2/1+6/1+12/1+20/1+30/1+42/1+56/1+72/1+90/1的答案

Question

如题所述

Answer 1

你把分子分母写倒了。二分之一应该写为：1/2
所以，你的式子应该是：
1/2
+
1/6
+
1/12
+
1/30
+
1/42
+
1/56
+
1/72
+
1/90
=
1/(1
*
2)
+
1/(2
*
3)
+
1/(3
*
4)
+
1/(4
*
5)
+
1/(5
*
6)
+
1/(6
*
7
+
1/(7
*
8)
+
1/(8
*
9)
+
1/(9
*
10)
=
(1
-
1/2)
+
(1/2
-
1/3)
+
(1/3
-
1/4)
+
(1/4
-
1/5)
+
(1/5
-
1/6)
+
(1/6
-
1/7)
+
(1/7
-
1/8)
+
(1/8
-
1/9)
+
(1/9
-
1/10)
=
1
-
1/10
=
9/10