Question

42分之1+56分之1+72分之1+90分之1+110分之1+132分之1的简便方法

Answer 1

解:

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

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

=1/6-1/12

=1/12