# Math Help - infinite prove

1. ## Re: infinite prove

Originally Posted by Burcin
I don't know what you mean do you mean that I cant prove proper that f is surjective?
Yes, you can. HallsofIvy just proved that f is surjective, but first he said what it means by definition.

Originally Posted by Burcin
So I don't neet to prove if f is surjective and injective to answer the question if 2|N is countably infinite
Yes, you do.

I would recommend reviewing or asking your instructor to explain how to prove statements of the form "For all x, P(x)" and "There exists an x such that P(x)." But above everything else, make sure that you know definitions by heart!

2. ## Re: infinite prove

I just learned all my definitions. I know understand everything thank you for the advice it really helped a lot

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