вправа 447 гдз 7 клас алгебра Мерзляк Полонський

Відповідь:

1) a(2a + b)(a + b) - 4a(a + b)² =
= (a + b)(a(2a + b) - 4a(a + b)) =
= (a + b)(2a² + ab - 4a² - 4ab) =
= -(a + b)(2a² + 3ab) =
= -a(a + b)(2a + 3b);
2) 3m²(m - 8) + 6m(m - 8)² =
= m(m - 8)(3m + 6(m - 8)) =
= m(m - 8)(9m - 48);
3) (2a + 3)(a + 5) + (a - 1)(a + 5) =
= (a + 5)(2a + 3 + a - 1) =
= (a + 5)(3a + 2);
4) (3x + 7)(4y - 1) - (4y - 1)(2x + 10) =
= (4y - 1)(3x + 7 - (2x + 10)) =
= (4y - 1)(3x + 7 - 2x - 10) =
= (4y - 1)(x - 3);
5) (5m - n)³(m + 8n)² -
- (5m - n)²(m + 8n)³ =
= (5m - n)²(m + 8n)²(5m - n - (m + 8n)) =
= (5m -n)²(m + 8n)²(5m - n - m - 8n) =
= (5m - n)²(m + 8n)²(4m - 9n).