The Composition of Surjective(Onto) Functions is Surjective Proof

The Composition of Surjective(Onto) Functions is Surjective Proof.

I included some pictures in the proof with the hope that perhaps it makes more sense.

[gainfulanalytics]

Thanks for this wonderful little example! Very

[amyagold]

this has confused me all semester thanks a lot

[jonathanjayes]

You're truly a wizard, thank you!

[FPrimeHD]

Really nice video. Having the map drawn out really helps. I am finding the hardest part for me in this class isn't the logic, it's turning my logic into words. How was you experience when you first started writing math proofs?

[livissocool]

Thanks so much!!!! This set (haha get it) of videos has saved me this unit.

[krumpy]

let f: X → Y, T ⊆ Y
can you prove that these following 3 statements are equivalent:
i) f is surjective,
ii) f(f^-1(T))=T for all T ⊆ Y,
iii) f(f^-1(Y))=Y .

Thanks!

[elgabos]

Shouldn´t the compositon of g: A to B and f: B to C be "g o f" instead of "f o g" ?

[mariodelrio]

Shouldn’t it be E! for that x€X at the recall? Like there’s just one element x from X that goes to an specific y, right?

[MichaelBrashier]

what is F is onto but G is not? is F o G onto?

[hasek]

I have a question, hope you can help.

It says that "Since g is onto, there exists a little a belonging to big A so that g(a)=b"

Isn't this true for all functions, though - not just surjective functions? Doesn't any function with a non-empty domain fulfill the requirement that there exists a number belonging to its domain such that this number maps to a number in the codomain?

Thank you