The question is:
A ball is thrown directly downward with an initial speed of 8.00m/s from a height of 30.0m. After what time interval does it strike the ground.
So I went through the problem and got the answer 1.79 sec. but after reviewing some notes from my teacher, I got the idea that in equations where an object is dropped down, the height has to be counted as negative. so I went through the problem again using -30m, but now my answer doesn't check out when plugged back in to x - x0 = V0 (t) + 1/2 at^2
Is there something I'm missing about this idea that height or distance is negative in drop-down questions?