\[\boxed{\text{800\ (800).}\text{\ }\text{Еуроки\ -\ ДЗ\ без\ мороки}}\]
Пояснение.
Решение.
\[\textbf{а)}\ (m + n)^{2} = m^{2} + 2mn + n^{2}\]
\[\textbf{б)}\ (c - d)^{2} = c^{2} - 2cd + d^{2}\]
\[\textbf{в)}\ (x + 9)^{2} = x^{2} + 2 \cdot 9x + 9^{2} =\]
\[= x^{2} + 18x + 81\]
\[\textbf{г)}\ (8 - a)^{2} = 8^{2} - 2 \cdot 8a + a^{2} =\]
\[= 64 - 16a + a^{2}\]
\[\textbf{д)}\ (a - 25)^{2} =\]
\[= a^{2} - 2 \cdot 25a + 25^{2} =\]
\[= a^{2} - 50a + 625\]
\[\textbf{е)}\ (40 + b)^{2} =\]
\[= 40^{2} + 2 \cdot 40b + b^{2} =\]
\(= 1600 + 80b + b^{2}\)
\[\textbf{ж)}\ (0,2 - x)^{2} =\]
\[= {0,2}^{2} - 2 \cdot 0,2x + x^{2} =\]
\[= 0,04 - 0,4x + x^{2}\]
\[\textbf{з)}\ (k - 0,5)^{2} =\]
\[= k^{2} - 2 \cdot 0,5k + {0,5}^{2} =\]
\[= k^{2} - k + 0,25\]