For the x part, I'm going to write x = x0 + v0 t.

对于 x 分量,有 x = x0 + v0 ? t.

耶鲁公开课 - 基础物理课程节选

if I say a particle's location is i times t^2 plus j times 9t^3, for every value of time, you can put the numbers in and you can find the velocity by just taking derivatives.

一个质点的位置,i ? t^2 + j ? 9t^3,在每一个时间点,你可以把数值代入,并通过求导得到速度

耶鲁公开课 - 基础物理课程节选