3.II .7E. 7 \mathrm{E} \quad

Groups | Part IA, 2008

Show that every Möbius map may be expressed as a composition of maps of the form z↦z+a,z↦λzz \mapsto z+a, z \mapsto \lambda z and z↦1/zz \mapsto 1 / z (where aa and λ\lambda are complex numbers).

Which of the following statements are true and which are false? Justify your answers.

(i) Every Möbius map that fixes ∞\infty may be expressed as a composition of maps of the form z↦z+az \mapsto z+a and z↦λzz \mapsto \lambda z (where aa and λ\lambda are complex numbers).

(ii) Every Möbius map that fixes 0 may be expressed as a composition of maps of the form z↦λzz \mapsto \lambda z and z↦1/zz \mapsto 1 / z (where λ\lambda is a complex number).

(iii) Every Möbius map may be expressed as a composition of maps of the form z↦z+az \mapsto z+a and z↦1/zz \mapsto 1 / z (where aa is a complex number).

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