(1)1/2*3+1/3*4+1/4*5.1/2006*2005 (2)1/2+1/(1+1)*(2+1)+1/(1+2)*(2+2).1/(1+2009)*(2+2009) (3)1+1/(1+2)+1/(1+2+3)+.1/(1+2+3+4.100)

(1)1/2*3+1/3*4+1/4*5.1/2006*2005 (2)1/2+1/(1+1)*(2+1)+1/(1+2)*(2+2).1/(1+2009)*(2+2009) (3)1+1/(1+2)+1/(1+2+3)+.1/(1+2+3+4.100)

(1)1/2*3+1/3*4+1/4*5.1/2006*2005=1/2 -1/3+1/3-1/4+1/4-1/5+.+/12005-1/2006=1/2 - 1/2006=1002/2006自己化簡一下.(2)1/2+1/(1+1)*(2+1)+1/(1+2)*(2+2).1/(1+2009)*(2+2009)=1/2+1/2-1/3+1/3…