b₄*b₆=1 b₄=?
b₄*b₆=(b₁*q)*(b₁*q⁵)=1
b₁²*q⁶=1
(b₁*q³)²=1
(b₄)²=1
b₄=-1 b₄=1.
b2*b6 = 1
b2 = b1*q; b4 = b1*q^3; b6 = b1*q^5
b1*q*b1*q^5 = (b1)^2*q^6 = 1
(b1*q^3)^2 = b4^2 = 1
b4 = 1 или - 1.
