题写颠倒了吧:
1/2 = 1 - 1/2, 1/6= 1/2 - 1/3, 1/12 = 1/3 - 1/4
其中的规律是: 2 = 1* 2, 6 = 2 * 3, 12 = 3 * 4, 20 = 4 * 5, 30 =5 * 6
1/2 + 1/6 + 1/12 + 1/20 + 1/30
= (1- 1/2) + (1/2 - 1/3) + (1/3 - 1/4) + (1/4 - 1/5) + (1/5 - 1/6)
= 1- 1/6
= 5/6
希望能帮到你。
题目中提示有错吧?好像应是1/2=1/1-1/2,1/6=1/2-1/3,1/12=1/3-1/4
解:1/2+1/6+1/12+1/20+1/30
=1-1/2+1/2-1/3+1/3-1/4+1/4-1/5+1/5-1/6
=1-1/6
=5/6
2/1+6/1+12/1+20/1+30/1=1-1/2+1/2-1/3+1/3-1/4+······+1/5-1/6
=1-1/6=5/6
1/2+1/6+1/12+1/20+1/30
=1-1/2+1/2-1/3+1/3-1/4+1/4-1/5+1/5-1/6
=1-1/6
=5/6
2/1+6/1+12/1+20/1+30/1
=1-2/1+2/1-3/1+3/1-4/1+4/1-5/1+5/1-6/1
=1-6/1
=6/5