\[\boxed{\text{679\ (679).}\text{\ }\text{Еуроки\ -\ ДЗ\ без\ мороки}}\]
Пояснение.
Решение.
\[\textbf{а)}\ (m - n)(x + c) =\]
\[= mx + mc - nx - nc\]
\[\textbf{б)}\ (k - p)(k - n) =\]
\[= k^{2} - kn - kp + pn\]
\[\textbf{в)}\ (a + 3)(a - 2) =\]
\[= a^{2} - 2a + 3a - 6 = a^{2} + a - 6\]
\[\textbf{г)}\ (5 - x)(4 - x) =\]
\[= 20 - 5x - 4x + x^{2} =\]
\[= x^{2} - 9x + 20\]
\[\textbf{д)}\ (1 - 2a)(3a + 1) =\]
\[= 3a + 1 - 6a^{2} - 2a =\]
\[= - 6a^{2} + a + 1\]
\[\textbf{е)}\ (6m - 3)(2 - 5m) =\]
\[= 12m - 30m^{2} - 6 + 15m =\]
\[= - 30m^{2} + 27m - 6\ \]