1.4(m-n)^2-9m^2
=[2(m-n)+3m][2(m-n)-3m]
=(5m-2n)(-m-2n)
=-(5m-2n)(m+2n)
2.-16m^3+16m^2-4m
=-4m(4m^2-4m+1)
=-4m(2m-1)(2m-1)
3.12m(x+y)^3-9n(x+y)^2
=3(x+y)^2*[4m(x+y)-3n]
=3(x+y)^2(4mx+4my-3n)
4.[a^2(2a+b)^2-9a^2b^2]/(a-b)
=a^2[(2a+b)^2-(3b)^2]/(a-b)
=a^2(2a+b+3b)(2a+b-3b)/(a-b)
=a^2(2a+4b)(2a-2b)/(a-b)
=4a^2(a+2b)