1) m + n/3mn : m^2n/m + n

2) y^2 - 25/3y^2 * 2y / 5 - y

(a^2-b^2) (a^2+b^2) = а^4-b^4

(5x^2-3y) (5x^2+3y) = 25x^4-9y^2

(3mn+1) (3mn-1) = 9m^2*n^2-1

(4pq+3) (3-4pq) = 9-16 (pq) ^2

(x^3+y^3) (x^3-y^3) = x^6-y^6

(4a^2+6b) (4a^2-6b) = 16a^4-36b^2

(5-7xy) (5+7xy) = 25-49 (xy) ^2

(2ab-5) (5+2ab) = 4 (ab) ^2-25

Формулф разности квадратов: (a-b) (a+b) = a^2-b^2