Question

2500/2x1+2500/2x3+2500/3x42500/ 4x5.2005/2004x2005怎么算?

Answer 1

原式=2005*(1/(2*1)+1/(3*2)+1/(4*3)+1/(5*4)+.+1/(2005*2004))=2005*((1-1/2)+(1/2-1/3)+(1/3-1/4)+(1/4-1/5)+.+(1/2004-1/2005))=2005*(1-1/2005)=2005*2004/2005=2004