(m-0.5n)(m+0.5n)-(3分之2n+m)(m-3分之2n)
=(m-1/2n)(m+1/2n)-(m+2/3n)(m-2/3n)
=m^2-(1/4)n^2-(m^2-4/9n^2)
=m^2-(1/4)n^2-m^2+(4/9)n^2
=(1/4+4/9)n^2
=(9/36+16/36)n^2
=(25/36)n^2
=[(5/6)n]^2