So what we're going to do is take the equations for those two lines, so here's one of those equations and here's the other one, set the P in those equations equal to X, I've got two equations in one unknown, I'm sorry, I've got one equation and one unknown.

接下来我们只需要,列出这两条线各自的方程,也就是这个方程和这个方程,把方程中的P换成X,我就得到了两个等式和一个未知数,错了,是一个等式和一个未知数

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