6) $$2\cdot \sqrt{1\frac{9}{16}} - 1 = 2 \cdot \sqrt{\frac{25}{16}} - 1 = 2 \cdot \frac{5}{4} - 1 = \frac{5}{2} - 1 = 2,5 - 1 = 1,5$$
Ответ: 1,5