Question

20分之1+30分之1+42分之1.+132分之1怎么做

Answer 1

解:

原式=1/(4*5)+1/(5*6)+1/(6*7)+1/(7*8)+1/(8*9)+1/(9*10)+1/(10*11)+1/(11*12)

=1/4-1/5+1/5-1/6+1/6-1/7+1/7-1/8+1/8-1/9+1/9-1/10+1/10-1/11+1/11-1/12

=1/4-1/12

=1/6