Question

2/1-6/1-12/1-20/1-30/1-42/1等于几？要写过程，越详细分越高

2/1读作2分之1，“/”代表分数线！在23:40之前发过来，必须对，要有明确的过程，才给分！拜托了！谢谢，快哦！

Answer 1

2/1-6/1-12/1-20/1-30/1-42/1
=2/1-(2/1-3/1)-(3/1-4/1)-(4/1-5/1)-(5/1-6/1)-(6/1-7/1)
=2/1-2/1+3/1-3/1+4/1-4/1+5/1-5/1+6/1-6/1+7/1
=7/1

Answer 2

原式=1/1*2-1/2*3-……-1/6*7
=1-1/2-1/2+1/3-……-1/6+1/7
=1/7

Answer 3

2/1-6/1-12/1-20/1-30/1-42/1
=2/1 -2/1+3/1 -3/1+4/1 -4/1+5/1 -5/1+ 6/1 -6/1+7/1
=7/1

Answer 4

1/2-1/6-1/12-1/30-1/42
=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
拆项相消法

(七分之一)