(2/3+2/9+2/27+2/81)-(1/2+1/4+1/8+1/16)
问题描述:
(2/3+2/9+2/27+2/81)-(1/2+1/4+1/8+1/16)
答
(2/3+2/9+2/27+2/81)-(1/2+1/4+1/8+1/16)
=(54/81+18/81+6/81+2/81)-(8/16+4/16+2/16+1/16)
=80/81-15/16
=(1-1/81)-(1-1/16)
=1/16-1/81
=65/1296