а) 25 - a2 = (5 - a)(5 + a)
б) 16x4 - 81 = (4x2 - 9)(4x2 + 9) = (2x - 3)(2x + 3)(4x2 + 9)
в) 0.25a2 - 0.09m4 = (0.5a - 0.3m2)(0.5a + 0.3m2)
г) 100 - 20a + a2 = (10 - a)2
д) 9y4 + 12y2z + 4z2 = (3y2 + 2z)2