[tex]16b _{1} = \frac{1}{16} \\ q = - 2 \\ b _{n} = b _{1} {q}^{n - 1} \\ \\ n = 3 \\ b _{3} = b _{1}q {}^{2} = \frac{1}{16} \times ( - 2) {}^{2} = \frac{4}{16} = \frac{1}{4} \\ \\ n = 5 \\ b _{5} = b _{1} {q}^{4} = \frac{1}{16} \times ( - 2) {}^{4} = \frac{16}{16} = 1[/tex]