Emissions per head: 17th in the world (9t of CO2 equivalent).

人均排放量：世界第17位(合9吨二氧化碳当量)。

youdao

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