(3m-a)(a+3m)-(2a+m)(3a-m) (x-4y)(x+3y)+(x-3y)(3y+x)

1) (3m - a) * (a + 3m) - (2a + m) * (3a - m) = 3am + 9m^2 - a^2 - 3am - (6a^2 - 2am + 3am - m^2) = 3am + 9m^2 - a^2 - 3am - 6a^2 + 2am - 3am + m^2 = (9m^2 + m^2) + (3am - 3am + 2am - 3am) + (- a^2 - 6a^2) = 10m^2 - am - 7a^2.

Ответ: 10m^2 - am - 7a^2.

2) (x - 4y) * (x + 3y) + (x - 3y) * (3y + x) = x^2 + 3xy - 4xy - 12y^2 + 3xy + x^2 - 9y^2 - 3xy = (x^2 + x^2) + (3xy - 4xy + 3xy - 3xy) + (- 12y^2 - 9y^2) = 2x^2 - xy - 21y^2.

Ответ: 2x^2 - xy - 21y^2.