(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