原式=(-2/3) +(+1/4) +(-1/6) +(-2/3)
=[ (-2/3)+(-2/3)+(-1/6) ] +(+1/4)
=[ -(2/3+2/3+1/6) ] +(+1/4)
=(-3/2)+(+1/4)
=-(3/2-1/4)
=-5/4
原式=(-2/3) +(+1/4) +(-1/6) +(-2/3)
=[ (-2/3)+(-2/3)+(-1/6) ] +(+1/4)
=[ -(2/3+2/3+1/6) ] +(+1/4)
=(-3/2)+(+1/4)
=-(3/2-1/4)
=-5/4