Вправи: 639

639. Подайте у вигляді добутку:

1) m³ + m²n – m – n = (m³ + m²n) – (m + n) = m²(m + n) – (m + n) = (m + n)(m² – 1) = (m + n)(m – 1)(m + 1);

2) ba² – 3a² – 4b + 12 = (ba² – 3a²) – (4b – 12) = a²(b – 3) – 4(b – 3) = (b – 3)(a² – 4) = (b – 3)(a – 2)(a + 2);

3) a³ – b³ + a – b = (a – b)(a² + ab + b²) + (a – b) = (a – b)(a² + ab

+ b² + 1);

4) x³ + 1 – 5x – 5 = (x + 1)(x² – x + 1) – 5(x + 1) = (x + 1) (x² – x +

+ 1 – 5) = (x + 1)(x² – x – 4).