а) 26 + (-6); б)-70+50; 5 и) + (8); 9 -- в) -17 + 30; г) 80 + (-120); 5 3 л)-+ ; 8 4' 3 2 K)+(-;)-+ 4 3 4 +; 2/3 3

Решение:

а) 26 + (-6) = 26 - 6 = 20

б) -70 + 50 = - (70 - 50) = -20

в) -17 + 30 = 30 - 17 = 13

г) 80 + (-120) = 80 - 120 = - (120 - 80) = -40

и) \(\frac{5}{9} + (-\frac{8}{9}) = \frac{5}{9} - \frac{8}{9} = \frac{5 - 8}{9} = \frac{-3}{9} = -\frac{1}{3}\)

л) \(-\frac{5}{8} + \frac{3}{4} = -\frac{5}{8} + \frac{3 \cdot 2}{4 \cdot 2} = -\frac{5}{8} + \frac{6}{8} = \frac{-5 + 6}{8} = \frac{1}{8}\)

к) \(\frac{3}{4} + (-\frac{2}{3}) = \frac{3}{4} - \frac{2}{3} = \frac{3 \cdot 3}{4 \cdot 3} - \frac{2 \cdot 4}{3 \cdot 4} = \frac{9}{12} - \frac{8}{12} = \frac{9 - 8}{12} = \frac{1}{12}\)

м) \(-\frac{4}{5} + \frac{2}{3} = -\frac{4 \cdot 3}{5 \cdot 3} + \frac{2 \cdot 5}{3 \cdot 5} = -\frac{12}{15} + \frac{10}{15} = \frac{-12 + 10}{15} = \frac{-2}{15} = -\frac{2}{15}\)