parabola

So, we should draw maybe this downward parabola.

我们可以画出这样的开口向下的抛物线。

From this one, you would not expect it to behave like a parabola.

从这一次，你不会期待它，如抛物线般运动。

It is perfectly reasonable to immediately come to that conclusion because of the symmetry of the parabola.

很理所应当的,由于抛物线的对称,立刻就会想到这个结论。