(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+1/3/4+1/4-1/5++++1/2005-1/2006=1/2-2006 스스로 간소화 한다.(2)1/2+1/(1+1)*(2+1)+1/(1+2)*(2+2).1/(1+2009)*(2+2009)=1/2+1/2+1/2+1/3+1/3...