-1的4次方-（1-0.5）*1/3*[2-(-3)的2次方] =1-0.5×1/3×（2-9）=1-1/6×7=1-6/7=1/7
-1的4次方-（1-0.5）*1/3*[2-(-3)的2次方] =1-0.5×1/3×[2-9]=1-1/6×(-7)=1-(-7/6)=13/6
