1. Muammoni tushuntirish: berilgan ifodalar ustida amallarni bajarish kerak: 28. $1 \tfrac{3}{7} (2.8a - 2.1) - 1 \tfrac{1}{9} (2.7a - 3.6)$ ni hisoblaymiz. 29. $1 \tfrac{2}{3} (1.5a - 4.5) - 1 \tfrac{3}{17} (3.4a + 5.1)$ ni hisoblaymiz. 30. $1.5 (4a - 6b) - 2 (3a - 2.5 (a - 4b))$ ni hisoblaymiz. 31. $1.8 (3a - (5b - 2a)) + 2.5 (2a - 4b)$ ni hisoblaymiz. 2. Har ifoda uchun quyi qadamlar: 28. - $1 \tfrac{3}{7} = \frac{10}{7}$ va $1 \tfrac{1}{9} = \frac{10}{9}$. - $\frac{10}{7} (2.8a - 2.1) - \frac{10}{9} (2.7a - 3.6)$ - Ko'paytiramiz: $\frac{10}{7} \times 2.8a = \frac{28}{7}a = 4a$, $\frac{10}{7} \times 2.1 = 3$. - Mantiqan to'g'ri yozish uchun vergul nuqtaga almashtiriladi: $2.8a = 2.8a$, $2.1 = 2.1$ ni 2.8a va 2.1 sifatida qabul qilamiz. - Shunga qarab, $\frac{10}{7} \times 2.8a = 4a$, $\frac{10}{7} \times 2.1 = 3$. - $\frac{10}{9} \times 2.7a = 3a$, $\frac{10}{9} \times 3.6 = 4$. - Natija: $(4a - 3) - (3a - 4) = 4a - 3 - 3a + 4 = a + 1$. 29. - $1 \tfrac{2}{3} = \frac{5}{3}$, $1 \tfrac{3}{17} = \frac{20}{17}$. - $\frac{5}{3} (1.5a - 4.5) - \frac{20}{17} (3.4a + 5.1)$. - Ko'paytiramiz: $\frac{5}{3} \times 1.5a = 2.5a$, $\frac{5}{3} \times 4.5 = 7.5$. - $\frac{20}{17} \times 3.4a \approx 4a$, $\frac{20}{17} \times 5.1 \approx 6$. - Natija: $2.5a - 7.5 - 4a - 6 = -1.5a - 13.5$. 30. - $1.5 (4a - 6b) - 2 (3a - 2.5 (a - 4b))$. - Ichki qavslarni yechamiz: $2.5 (a - 4b) = 2.5a - 10b$. - $3a - (2.5a - 10b) = 3a - 2.5a + 10b = 0.5a + 10b$. - $1.5 (4a - 6b) - 2 (0.5a + 10b) = 6a - 9b - (1a + 20b) = 6a - 9b -1a - 20b = 5a - 29b$. 31. - $1.8 (3a - (5b - 2a)) + 2.5 (2a - 4b)$. - Ichki qavslarni yechamiz: $3a - 5b + 2a = 5a - 5b$. - $1.8 (5a - 5b) + 2.5 (2a - 4b) = 9a - 9b + 5a - 10b = 14a - 19b$. 3. Yechimlar: - 28. $a + 1$ - 29. $-1.5a - 13.5$ - 30. $5a - 29b$ - 31. $14a - 19b$