Вариант №3 Упростите выражения. 1) 6x+y-x- 8y; 2) (18,6 + 3a) - (0,26 + 5a); 3) (\(\frac{3}{8}\)a + b) + (-\(\frac{3}{8}\)a - \(\frac{1}{7}\)b); 4) 5(2x + 4) - 3(7x + 9) - 3; 5) 5(1\(\frac{2}{5}\)m - 0,6) + 2(1,3 - \(\frac{7}{8}\)m).

Решение:

1. \( 6x + y - x - 8y = (6x - x) + (y - 8y) = 5x - 7y \)
2. \( (18,6 + 3a) - (0,26 + 5a) = 18,6 + 3a - 0,26 - 5a = (18,6 - 0,26) + (3a - 5a) = 18,34 - 2a \)
3. \( (\(\frac{3}{8}\)a + b) + (-\(\frac{3}{8}\)a - \(\frac{1}{7}\)b) = \(\frac{3}{8}\)a + b - \(\frac{3}{8}\)a - \(\frac{1}{7}\)b = (\(\frac{3}{8}\)a - \(\frac{3}{8}\)a) + (b - \(\frac{1}{7}\)b) = 0 + \(\frac{6}{7}\)b = \(\frac{6}{7}\)b \)
4. \( 5(2x + 4) - 3(7x + 9) - 3 = 10x + 20 - 21x - 27 - 3 = (10x - 21x) + (20 - 27 - 3) = -11x - 10 \)
5. \( 5(1\(\frac{2}{5}\)m - 0,6) + 2(1,3 - \(\frac{7}{8}\)m) = 5(\(\frac{7}{5}\)m - \(\frac{3}{5}\)) + 2(\(\frac{13}{10}\) - \(\frac{7}{8}\)m) = \( 7m - 3 \) + \( \frac{13}{5} \) - \( \frac{7}{4}m \) = (7m - \( \frac{7}{4}m \)) + (\( \frac{13}{5} \) - 3) = (\( \frac{28-7}{4} \)m) + (\( \frac{13-15}{5} \)) = \( \frac{21}{4}m \) - \( \frac{2}{5} \) \)

Ответ: 1) 5x - 7y; 2) 18,34 - 2a; 3) \(\frac{6}{7}\)b; 4) -11x - 10; 5) \( \frac{21}{4}m \) - \( \frac{2}{5} \).