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8.4: Let f : X → Y and g : Y→ Z be maps. Prove that...

8.4: Let f : X → Y and g : Y→ Z be maps. Prove that if composition g o f is surjective then g is surjective.

8.5: Let f : X → Y and g : Y→ Z be bijections. Prove that if composition g o f is bijective then f is bijective.

8.6: Let f : X → Y and g : Y→ Z be maps. Prove that if composition g o f is bijective then f is injective and g is surjective.

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