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So, for example, if we're to hold the time constant, this makes it a lot simpler of an equation, because what we can end up doing is actually crossing out this whole term here.
比如说，如果我们把时间,定为常数，这使得方程,大大简化，因为我们可以把,这一项划掉。
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You can go ahead and use that equation, or you could figure it out every time, because if you know the total number of nodes, and you know the angular node number, then you know how many nodes you're going to have left.
你们可以直接用这个方程，或者每次都自己算出来，因为如果你们知道了总的节点数，又知道角向节点数，就知道剩下的节点数是多少。
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So the trick is to eliminate time from this equation.
所以这里的技巧就是消去方程中的时间
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Some will be growing very rapidly, some will be growing less rapidly, and what this equation shows you here or that rate of growth the to the doubling time of cells.
有些会生长得更快些,有的慢一些,而这个方程告诉你,即生长的速率和细胞倍增的时间联系起来
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And the mathematics of that equation involved a double derivative in time of x 0 plus some constant times x equals zero with some constraints on it.
那个数学方程式,包括了x对时间的二阶导数,加上常数乘以x等于,还有一些限制条件。
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And we talked about the equation you can use for radial nodes last time, and that's just n minus 1 minus l.
我们讲过这个用于,计算径向节点的方程，也就是ｎ减去ｌ减去１
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And the reason is, and this will come up on the problems and a lot of students end up using this equation, which is why I want to head it off and mention it ahead of time, we can't use an equation because this equation is very specific for light.
原因是，很多同学在解题时,都会用这个方程，所以我要,事先提醒你们一下,我们不能用这个方程，因为它只对光是用。
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c We know it's very specific for light because in this equation is c, the speed of light. So any time you go to use this equation, if you're trying to use it for an electron, just ask yourself first, does an electron travel at the speed of light?
我们知道它只对光适用是因为在这个方程里有,光速，所以下次你们用这个方程前，如果你们要把它用到一个电子上，先问问你自己，电子的运动速度是光速吗？
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Then go to the x equation and demand that this be equal to the desired x value and find the time.
然后列出关于 x 的方程,令这个式子等于给定的 x,并求出时间
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