I just take the derivative of this answer,

我只要对这个式子求导
which is 10-10t.

得到10-10t
So let me pick a couple of trivial questions one can ask.

现在我提出一些常见的问题
One can ask the following question.

有人会这么问
How high does it go?

它能跑到多高的地方
How high will it rise? To what height will it rise?

它能运动多高
So, we know it's going to go up and turn around and come down.

我们知道物体会先上升然后调转方向下落
We're trying to see how high that is.

我们来计算最高点在哪儿
So, that is a tricky problem to begin with

所以这个问题刚开始的时候有点难度
because if you take this formula here,

因为如果你要用这个公式
it tells you y if you know t,

求y的时候就一定要知道t
but no, we're not saying that.

但是我们不知道