8) 1/5 a²b² + 2/5 a²b+ 3/5 ab² + 4/5 a²b² =

Приведем подобные члены:

$$\frac{1}{5}a^2b^2 + \frac{2}{5}a^2b + \frac{3}{5}ab^2 + \frac{4}{5}a^2b^2 = (\frac{1}{5} + \frac{4}{5})a^2b^2 + \frac{2}{5}a^2b + \frac{3}{5}ab^2 = \frac{5}{5}a^2b^2 + \frac{2}{5}a^2b + \frac{3}{5}ab^2 = a^2b^2 + \frac{2}{5}a^2b + \frac{3}{5}ab^2$$

Ответ: $$a^2b^2 + \frac{2}{5}a^2b + \frac{3}{5}ab^2$$