when solving an inequality and you have to take the square root of both sides, what is the rule for the changing of the inequality sign?

if the number was between 0 and 1, then the sign would need changing, but if it were greater than 1, it wouldnt

same goes for 0 and -1.

for example:

-9 < 16x^2

that turns into: 3i < 4x

but im unsure because the rules would differ for the above mentioned numbers.

helppp