3 - 2 = 1；5 - 4 = 1....101 - 100 =1原式= 1+50×1=51
=1+(3-2)+(5-4)+...+(99-98)+(101-100)=1+50=51
重新组合=(1-2)+(3-4)+(5-6)+...+(99-100)+101=-1-1-1-...-1+101前面一共1-100,100个数两两一组有50组所以50个-1所以=101-50=51
