=(2m-3)^2-n^2

=4m^2- 12m+9-n^2

(2)(-3x+y+z)×(-3x-y-z)

=(-3x)^2-(y+z)^2

=9x^2-y^2-2yz-z^2

(3)(3a+2 B- 1)×(3a-2 b+ 1)

=(3a)^2-(2b- 1)^2

=9a^2-4b^2+4b- 1

The factor can be decomposed by the square difference formula: a 2-b 2 = (a-b) (a+b).