(-1 1/2)17/(-1 1/2)15 =

$$\frac{(-1 \frac{1}{2})^{17}}{(-1 \frac{1}{2})^{15}} = (-1 \frac{1}{2})^{17-15} = (-1 \frac{1}{2})^2 = (-\frac{3}{2})^2 = \frac{9}{4} = 2 \frac{1}{4} = 2.25$$.

Ответ: $$2.25$$