A.a=d(b≠D. B.b=a(b≠D. C.a=c(b=D. D.b=c(b≠D.
A.a²c=-1 B.a²c=1 C.a²d=-1 D.b²c=-1
A.a=d(b≠D. B.b=a(b≠D. C.a=c(b≠D. D.b=c(b≠D.