(-8/9)×(-0.25)×(-1/4)×9=(-8/9)*9*(-0.25)*(-1/4)=(-1)*1=-1(1又3/4-0.875-7/12)×(-1又1/7)=(7/4-7/8-7/12)*(-8/7)打开=(-2)+1+3/4=-1/4(-5)×(-7/9)×(-0.8)×(2又1/4)×(-1/7)=[(-5)*(-0.8)]*[(-7/9)*(-1/7)]*(9/4)=4*(1/9)*(9/4)=1