(-1又2分之一)乘(-1又3分之1)乘(-1又4分之1)乘(-1又5分之1)乘(-1又6分之一)
=-3/2*4/3*5/4*6/5*7/6
=-7/2
=-3.5
(1/4+1/6-1/2)*48
=1/4*48+1/6*48-1/2*48
=12+8-24
=-4