Приведите подобные слагаемые:
а) $\frac{2}{3}b + \frac{19}{21}b$;
б) $-\frac{2}{3}b - \frac{19}{21}b$;
в) $-\frac{2}{3}b + \frac{19}{21}b$;
г) $\frac{2}{3}b - \frac{19}{21}b$;
д) $\frac{1}{2}a + \frac{3}{5}a$;
е) $\frac{1}{2}a - \frac{3}{5}a$.
$\frac{2}{3}b + \frac{19}{21}b = \frac{14}{21}b + \frac{19}{21}b = \frac{33}{21}b = 1\frac{12}{21}b$
$-\frac{2}{3}b - \frac{19}{21}b = -\frac{14}{21}b - \frac{19}{21}b = -\frac{33}{21}b = -1\frac{12}{21}b$
$-\frac{2}{3}b + \frac{19}{21}b = -\frac{14}{21}b + \frac{19}{21}b = \frac{5}{21}b$
$\frac{2}{3}b - \frac{19}{21}b = \frac{14}{21}b - \frac{19}{21}b = -\frac{5}{21}b$
$\frac{1}{2}a + \frac{3}{5}a = \frac{5}{10}a + \frac{6}{10}a = \frac{11}{10}a = 1\frac{1}{10}a$
$\frac{1}{2}a - \frac{3}{5}a = \frac{5}{10}a - \frac{6}{10}a = -\frac{1}{10}a$
Пожауйста, оцените решение