简便计算:1/2+3/4+7/8+15/16+31/32+63/64+127/128+255/256
问题描述:
简便计算:1/2+3/4+7/8+15/16+31/32+63/64+127/128+255/256
答
设
a=1/2+3/4+7/8+15/16+31/32+63/64+127/128+255/256
b=1/2+1/4+1/8+1/16+ 1/32+1/64+ 1/128+1/256
那么a+b=8
b+1/256=1/2+1/4+1/8+1/16+ 1/32+1/64+ 1/128+(1/256+1/256)
=1/2+1/4+1/8+1/16+ 1/32+1/64+( 1/128+1/128)
=1/2+1/4+1/8+1/16+ 1/32+(1/64+ 1/64)
=……
=1
所以b=1-1/256
a=8-b=8-(1-1/256)
=7+1/256