(x^2-(m-n)x-mn)\(x^2+(m-n)x-mn)*(x^2-n^2)\(x^2-m^2)
=(x-m)(x+n)/[(x+m)(x-n)]*[(x-n)(x+n)]/[(x-m)(x+m)]
=(x+n)^2/(x+m)^2
=(2-1/2)^2/(2+3)^2
=(9/4)/25
=9/100