In terms of how best to structure (word) each of these hypotheses, consider the following hypothetical examples (parenthetical information is added to clarify the level of measurement of X and Y and should not appear in your hypotheses):
Positive: "As X increases, Y increases" or "As X decreases, Y decreases" (Be sure the direction of X and Y is the same)
Negative: "As X increases, Y decreases" or "As X decreases, Y increases" (Be sure the direction of X and Y are inverse or the opposite)
Finally, you should recall that, as a researcher, you determine if the relationship between X and Y is positive or negative based on your understanding of prior research.
I hope this helps!