Требуется решить 4 и 7 задание

#4. 81c² - d² + 9c + d = (9c - d)(9c + d) + (9c + d) = (9c + d)(9c - d + 1) 

25 - m² - 12mn - 36n² = 25 - (m² + 2*6*m*n + 36n²) = 25 - (m + 6n)² = 5² - (m + 6n)² = (5 - m - 6n)(5 + m + 6n) 

(x + 2)³ - 125 = (x + 2)³ - 5³ = (x + 2 - 5)((x + 2)² -  5(x+2) + 5²) = (x - 3)(x² + 4x + 4 - 5x - 10 + 25) = (x-3)(x² - x + 19)

#7. y³ + 3y²z + 3yz² + 2z³ = y³ + 3y²z + 3yz² + z³ + z³ = (y + z)³ + z³ = (y+z+z)(y²  - yz + z²)