m-1分之1-2m+m的平方-m的平方-m分之m-1
=（m-1）²/(m-1)-(m-1)/m(m-1)
=m-1-1/m
=(m²-m-1)/m
=(3-√3-1)/√3
=(2-√3)/√3
=√3(2-√3)/3
=(2√3-3)/3
=2/3√3-1