Crowley said the Obama administration wants the meeting - presumably at the level of Foreign Ministry political directors to be held as soon as possible, so that P5+1 leaders can assess Iran's readiness to deal with the nuclear issue in their discussions at the United Nations.

VOA: standard.2009.09.11

Then, to find the meaning of b, we take one derivative of this, dx/dt, that's velocity as a function of time, and if you took the derivative of this guy, you will find as at+b. That's the velocity of the object.

接下来,为了弄清b的含义,我们取它的一阶导数,dx/dt,得到速度作为时间的函数,如果你对它求导的话,你会得到at+b,这就是物体的速度

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