1) (5a+6)^2-81 2)9m^2-(1+2m)^2 3) (5c-3d)^2-9d^2

1) =(5a+6-9)(5a+6+9)=(5a-3)(5a+15)2) =(3m-(1+2m))(3m+1+2m)=(3m-1-2m)(5m+1)=(m-1)(5m+1)3) =(5c-3d -3d)(5c-3d+3d)=(5c-6d)*5c=5c(5c-6d)