(1+3m)(1-3m)=1-9m
(2x-1)(2x+1)=4x^2-1
(2x-y)(2x+y)=4x^2-y^2
1) (1+3m)(1-3m)=1-9m^2
2) (2x-1)(2x+1)=4x^2-1
3) (2x-y)(2x+y)=4x^2-y^2
(1+3m)(1-3m)=1-9m
(2x-1)(2x+1)=4x^2-1
(2x-y)(2x+y)=4x^2-y^2
1) (1+3m)(1-3m)=1-9m^2
2) (2x-1)(2x+1)=4x^2-1
3) (2x-y)(2x+y)=4x^2-y^2