\[\boxed{\text{678\ (678).}\text{\ }\text{Еуроки\ -\ ДЗ\ без\ мороки}}\]
Пояснение.
Решение.
\[\textbf{а)}\ (x + 6)(x + 5) =\]
\[= x^{2} + 5x + 6x + 30 =\]
\[= x^{2} + 11x + 30\]
\[\textbf{б)}\ (a - 4)(a + 1) =\]
\[= a^{2} + a - 4a - 4 =\]
\[= a^{2} - 3a - 4\]
\[\textbf{в)}\ (2 - y)(y - 8) =\]
\[= 2y - 16 - y^{2} + 8y =\]
\[= - y^{2} + 10y - 16\]
\[\textbf{г)}\ (a - 4)(2a + 1) =\]
\[= 2a^{2} + a - 8a - 4 =\]
\[= 2a^{2} - 7a - 4\]
\[\textbf{д)}\ (2y - 1)(3y + 2) =\]
\[= 6y^{2} + 4y - 3y - 2 =\]
\[= 6y^{2} + y - 2\]
\[\textbf{е)}(5x - 3)(4 - 3x) =\]
\[= 20x - 15x^{2} - 12 + 9x =\]
\[= - 15x^{2} + 29x - 12\ \]