1/3+1/(3+6)+1/(3+6+9)+1/(3+6+9+12)+1/(3+6+9+12+15)+.1/(3+6+9+12+1_数学解答

1/3+1/(3+6)+1/(3+6+9)+1/(3+6+9+12)+1/(3+6+9+12+15)+.1/(3+6+9+12+15+.96+99)

人气：459 ℃　时间：2020-04-18 05:12:45

解答

=( 1/1+1/(1+2)+````+1/(1+2+3`+```+33) ) /3
=( 2/1*2+2/2+3+2/3*4+...+2/33*34 ) /3
=2/3 (1-1/2+1/2-1/3+1/3-1/4.+1/33-1/34)
=2/3 (33/34)
=11/17
原理等差求和公式+列项求和