两边同乘以2
2x-x=5/4
x=5/42/1+4/1+8/1+16/1+64/1+128/1+256/1+512/1z怎么简算呀令a=2/1+4/1+8/1+16/1+64/1+128/1+256/1+512/12a=1+2/1+4/1+8/1+16/1+64/1+128/1+256/1相减2a-a=1-512/1所以a=512/511