вправа 392 гдз 7 клас алгебра Мерзляк Полонський

Відповідь:

1) (a - 2)(b + 5) =
= ab + 5a - 2b - 10;
2) (m + n)(p - k) =
= mp - mk + np - nk;
3) (x - 8)(x + 4) =
= x² + 4x - 8x - 32 =
= x² - 4x - 32;
4) (x - 10)(x - 9) =
= x² - 9x - 10x + 90 =
= x² - 19x + 90;
5) (c + 5)(c + 8) =
= c² + 8c + 5c + 40 =
= c² + 13c + 40;
6) (3y + 1)(4y - 6) =
= 12y² - 18y + 4y - 6 =
= 12y² - 14y - 6;
7) (-2m - 3)(5 - m) =
= -10m + 2m² - 15 + 3m =
= 2m² - 7m - 15; \begin{equation}8)\left ( 5x^{2}-x \right )\left ( 6x^{2}+4x \right )=\end{equation} \begin{equation}=30x^{4}+20x^{3}-\end{equation} \begin{equation}-6x^{3}-4x^{2}=\end{equation} \begin{equation}=30x^{4}+14x^{3}-4x^{2};\end{equation} \begin{equation}9)\left ( -c-4 \right )\left ( c^{3} +3\right )=\end{equation} \begin{equation}=-c^{4}-3c-4c^{3}-12=\end{equation} \begin{equation}=-c^{4}-4c^{3}-3c-12;\end{equation} 10) (x - 5)(x² + 4x - 3) =
= x³ + 4x² - 3x - 5x² - 20x + 15 =
= x³ - x² - 23x + 15;
11) (2a + 3)(4a² - 4a + 3) =
= 8a³ - 8a² + 6a + 12a² - 12a + 9 =
= 8a³ + 4a² - 6a + 9;
12) a(5a - 4)(3a - 2) =
= (5a² - 4a)(3a - 2) =
= 15a³ - 10a² - 12a² + 8a =
= 15a³ - 22a² + 8a.