As you put it, the equivalence just isn't true. So, don't feel bad about not understanding it. To see, let's take an example. Let's say we have booleans only, N=6
and K=2
, and the assignment:
True False False False False False
to these 6 variables. The statement At most 2 out of 6 are True
is obviously satisfied by this assignment, but At least 4 out of 6 are True
is not.
Maybe what you meant is:
at least K out of N is True
is equivalent to
at most N-K out of N is False
which can be further generalized to say:
at least K out of N objects have property P
is equivalent to:
at most N-K out of N objects do not have the property P
Is this what you were trying to express? Hope that's more clear!