№5. Сложите подобные слагаемые: a) −9x + 7x − 5x + 2x; б) 5a − 6a + 2a − 10a; в) 11p + 2p + 20p − 7p; г) −3,8k − k + 3,8k + k; д) a + 6,2a − 6,5a − a; e) −18n − 12n + 7,3n + 6,5n; ж) \(\frac{2}{9}\)m + \(\frac{2}{9}\)m − \(\frac{3}{9}\)m − \(\frac{5}{9}\)m; з) \(\frac{2}{3}\)a − \(\frac{1}{6}\)a + \(\frac{1}{2}\)a − \(\frac{1}{12}\)a; и) b + 0,4b − \(\frac{1}{5}\)b − \(\frac{1}{2}\)b.

Решение:

№5.

1. \(-9x + 7x − 5x + 2x = (-9+7-5+2)x = -5x\)
2. \(5a − 6a + 2a − 10a = (5-6+2-10)a = -9a\)
3. \(11p + 2p + 20p − 7p = (11+2+20-7)p = 26p\)
4. \(-3,8k − k + 3,8k + k = (-3,8-1+3,8+1)k = 0k = 0\)
5. \(a + 6,2a − 6,5a − a = (1+6,2-6,5-1)a = -0,3a\)
6. \(-18n − 12n + 7,3n + 6,5n = (-18-12+7,3+6,5)n = -16,2n\)
7. \(\frac{2}{9}m + \frac{2}{9}m − \frac{3}{9}m − \frac{5}{9}m = (\frac{2}{9} + \frac{2}{9} - \frac{3}{9} - \frac{5}{9})m = \frac{4-8}{9}m = -\frac{4}{9}m\)
8. \(\frac{2}{3}a − \frac{1}{6}a + \frac{1}{2}a − \frac{1}{12}a = (\frac{2}{3} - \frac{1}{6} + \frac{1}{2} - \frac{1}{12})a = (\frac{8}{12} - \frac{2}{12} + \frac{6}{12} - \frac{1}{12})a = \frac{8-2+6-1}{12}a = \frac{11}{12}a\)
9. \(b + 0,4b − \frac{1}{5}b − \frac{1}{2}b = (1 + 0,4 - 0,2 - 0,5)b = 0,7b\)