k1, k2, m1, m2 are cardinal numbers.
I need to prove that if k2>=k1 and m2>=m1, then k2m2>=k1m1
I know that i need to prove that this function f:AXC->BxD is injective, but then what?
Thanks for any help :-)
I mean I think you are already pretty much done. I am guessing from your notation this is what you mean. You know since and then there must exist injective functions and . But then it is pretty obvious that defined by would also be injective. Just write out definitions and it is clear.