12/1+23/1+34/1+.20112012/1之和等于多少啦

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1*2/1+2*3/1+3*4/1+.2011*2012/1之和等于多少啦
1*2/1+2*3/1+3*4/1+.2011*2012/1之和等于多少啦

1*2/1+2*3/1+3*4/1+.2011*2012/1之和等于多少啦
1/1*2+1/2*3+1/3*4+.+1/2011*2012
=1-1/2+1/2-1/3+1/3-1/4+.+1/2011-1/2012
=1-1/2012
=2011/2012

1*2/1+2*3/1+3*4/1+......2011*2012/1
=（1-1/2）+（1/2-1/3）+（1/3-1/4）+...+（1/2011-1/2012）
=1-1/2012
=2011/2012

1*2/1+2*3/1+3*4/1+......2011*2012/1
反一个身
1/1*2+1/2*3+1/3*4+1/4*5+……+1/2011*2012
=1-1/2+1/2-1/3+1/3-1/4+1/4+……-1/2011+1/2011-1/2012
=1-1/2012
=2011/2012

(1-1/2^2)(1-1/3^2)(1-1/4^2).(1-1/2009^2), 1+2+3+4+1 1/(2^3)+1/(2^3+1)+1/(2^3+2)+1/(2^3+3)+...+1/(2^4-1) 1 2 3 4 1 2 3 4 1 2 3 4 1,2,3,4, 1 2 3 4 1 2 3 4 1,2,3,4, 1,2,3,4, 1,2,3,4, 1,2,3,4, 1 2 3 4 1,2,3,4, 1,2,3,4, 1,2,3,4, 1、2、3、4