4)10a+6b 6b-a. 11a³ 11a³

4) $$\frac{10a + 6b}{11a^3} - \frac{6b - a}{11a^3} = \frac{10a + 6b - 6b + a}{11a^3} = \frac{11a}{11a^3} = \frac{1}{a^2}.$$

Ответ: $$\frac{1}{a^2}$$