(-2/5)+(-5/6)-(-4.9)-0.6
=-2/5-5/6+4.9-0.6
=-37/36+4.3
=4+3/10-37/36
=3又180分之49
(1-2)(3-4)(4-5)(5-6)...(103-104)
=(-1)(-1)(-1)...(-1)
有52个,52是偶数
所以=1