(0.91 1循环+0.82 2循环+0.73 3循环+0.64 4循环)-(0.1 1循环+0.2 2循环+0.3 3循环+0.4 4循环+0.5 5循环+0.6 6循环)
=(0.9+0.8+0.7+0.6)+(1/90+2/90+3/90+4/90)-(1/9+2/9+3/9+4/9+5/9+6/9)
=3+1/9-7/3
=7/9
(0.91 1循环+0.82 2循环+0.73 3循环+0.64 4循环)-(0.1 1循环+0.2 2循环+0.3 3循环+0.4 4循环+0.5 5循环+0.6 6循环)
=(0.9+0.8+0.7+0.6)+(1/90+2/90+3/90+4/90)-(1/9+2/9+3/9+4/9+5/9+6/9)
=3+1/9-7/3
=7/9