b₇ = 2⁻¹²; b₉ =  2⁻¹⁴.

q⁹⁻⁷ = b₉/b₇; q² = 2⁻¹⁴/2⁻¹²; q² = 2⁻²; q = 2⁻¹; q = 1/2.

b₇ = b₁q⁶; b₁ = b₇/q⁶; b₁ = 2⁻¹²/(1/2)⁶ = 2⁻¹² · 2⁶ = 2⁻⁶ = 1/2⁶ = 1/64;