因为|m-1/2|=0
所以 m =1/2
把m=1/2带入代数式4m^2-{6m-2(3m+2)-2m^2},得：
4×1/2^2-｛6×1/2-2(3×1/2+2)-2×1/2^2}
=1-{3-7-1/2}
=1-3+7+1/2
=-2+7+1/2
=5+1/2
=五又二分之一