(4x^2-12xy+9y^2)^-4/[(3xy-2x^2)^-2]^-3
=(2x-3y)^-8/(3xy-2x^2)^6
=(2x-3y)^-8/[x(3y-2x)^6]
=(2x-3y)^-8/[x^6(3y-2x)^6]
=(2x-3y)^-14/(-x^6)
=1/[(-x^6)(2x-3y)^-14]
[-3a^(n+1）]^-2/[a^(n+2)×（a^n×b^2)^-3]
=[-3a^(n+1）]^-2/[a^(n+2)×（a^-3n×b^-6)]
=[-3a^(-2n-2)]/[a^(-2n+2)b^(-6)]
=[-3a^(-2n)/(-3a)^2)]/[a^(-2n)*a^2)b^(-6)]
=[-3a^(-2n)]/[(-3a)^2)*a^(-2n)*a^2)b^(-6)]
=(-3)/[(-3a)^2)*a^2b^(-6)]
=1/[a^4b^(-6)]
=1/a^4*b^6
=b^6/a^4