[see also: correct, valid, hold
The conjecture (now known not to be true in general) was that......
In other algorithms, this may not be true.
Unfortunately, because of the possible presence of “cusps'', this need not be true.
This is not true of F. [Or: for F]
This works regardless of whether B is true or false.
Let us now take a quick look at the class N, with the purpose of determining how much of Theorems 1 and 2 is true here.
This suggests a question: under what conditions is it true that......?
Only in exceptional circumstances is it true that f(x+y)=f(x)+f(y). [Note the inversion.]