1/2*1+1/2*3+1/3*4+.+1/2004*2005=?

1/2*1+1/2*3+1/3*4+.+1/2004*2005=?

1/2*1+1/2*3+1/3*4+.+1/2004*2005
=1-1/2+1/2-1/3+...+1/2004-1/2005
=1-1/2005
=2004/2005;
Split term method: 1 / N × (n + 1) = 1 / n-1 / (n + 1);
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The first line: 1; the second line: negative half, one third; the third line: negative quarter, one fifth, one sixth; so what is the N line
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1
-1/2
1/3
-1/4
1/5
-1/6
(- 1) ^ (n + 1) / n

In one third, two fifths, three eighths and four fifths, is the number greater than one fourth but less than one half right?

All of them