Задание 4. Найдите значение выражения: 1) 1/(1/36+1/44); 2) 1/(1/36−1/44); 3) 1/(1/36+1/45); 4) 1/(1/35−1/60); 5) 1/(1/21+1/28); 6) 1/(1/72−1/99).

1. \(\frac{1}{\frac{1}{36}+\frac{1}{44}}=\frac{1}{\frac{11+9}{396}}=\frac{396}{20}=\frac{99}{5}\).
2. \(\frac{1}{\frac{1}{36}-\frac{1}{44}}=\frac{1}{\frac{44-36}{1584}}=198\).
3. \(\frac{1}{\frac{1}{36}+\frac{1}{45}}=\frac{1}{\frac{5+4}{180}}=20\).
4. \(\frac{1}{\frac{1}{35}-\frac{1}{60}}=\frac{1}{\frac{12-7}{420}}=84\).
5. \(\frac{1}{\frac{1}{21}+\frac{1}{28}}=\frac{1}{\frac{4+3}{84}}=12\).
6. \(\frac{1}{\frac{1}{72}-\frac{1}{99}}=\frac{1}{\frac{99-72}{7128}}=264\).

Ответ: 1) 99/5; 2) 198; 3) 20; 4) 84; 5) 12; 6) 264.