1980/(1*2*3)+1980/(2*3*4)+1980/(3*4*5)+…+1980/(98*99*100)=?

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1980/(1*2*3)+1980/(2*3*4)+1980/(3*4*5)+…+1980/(98*99*100)=?1980/(1*2*3)+1980/(2*3*4)+1980/(3*4*5)+…+

1980/(1*2*3)+1980/(2*3*4)+1980/(3*4*5)+…+1980/(98*99*100)=?
1980/(1*2*3)+1980/(2*3*4)+1980/(3*4*5)+…+1980/(98*99*100)=?

1980/(1*2*3)+1980/(2*3*4)+1980/(3*4*5)+…+1980/(98*99*100)=?
原式=1980/2*(1/1-2/2+1/3+1/2-2/3+1/4+1/3-2/4+1/5+...1/98-2/99+1/100)
=1980/2*(1+1/2-1/99+1/100)
=14849/10