вправа 393 гдз 7 клас алгебра Мерзляк Полонський

Відповідь:

1) (a + b)(c - d) =
= ac - ad + bc - bd;
2) (x - 6)(x - 4) =
= x² - 4x - 6x + 24 =
= x² - 10x + 24;
3) (a - 3)(a + 7) =
= a² + 7a - 3a - 21 =
= a² + 4a - 21;
4) (11 - c)(c + 8) =
= 11c + 88 - c² - 8c =
= -c² + 3c + 88;
5) (d + 13)(2d - 1) =
= 2d² - d + 26d - 13 =
= 2d² + 25d - 13;
6) (3y - 5)(2y - 12) =
= 6y² - 36y - 10y + 60 =
= 6y² - 46y + 60; \begin{equation}7)\left ( 2x^{2}-3 \right )\left ( x^{2}+4 \right )=\end{equation} \begin{equation}=2x^{4}+8x^{2}-3x^{2}-12=\end{equation} \begin{equation}=2x^{4}+5x^{2}-12;\end{equation} 8) (x - 6)(x² - 2x + 9) =
= x³ - 2x² + 9x - 6x² + 12x - 54 =
= x³ - 8x² + 21x - 54;
9) (5x - y)(2x² + xy - 3y²) =
= 10x³ + 5x²y - 15xy² - 2x²y - xy² + 3y³ =
= 10x³ + 3x²y - 16xy² + 3y³;
10) b(6b + 7)(3b - 4) =
= (6b² + 7b)(3b - 4) =
= 18b³ - 24b² + 21b² - 28b =
= 18b³ - 3b² - 28b.