设x=5/2+9/4+17/8+33/16+65/32+129/64-13.
则2x=5+9/2+17/4+33/8+65/16+129/32-26.
故x=2x-x
=5+9/2+17/4+33/8+65/16+129/32-26
-(5/2+9/4+17/8+33/16+65/32+129/64-13)
=5+9/2+17/4+33/8+65/16+129/32-26
-5/2 -9/4- 17/8 -33/16 -65/32-129/64+13
用错位相减法
=5+4/2+8/4+16/8+32/16+64/32-129/64-13
=5+2+2+2+2+2-13-129/64
=2-129/64
=-1/64.
故5/2+9/4+17/8+33/16+65/32+129/64-13==-1/64