/v？ ct=30 1989888。 rn=20。 pn = 0 & ampdb = 0 & amps = 8 & ampword = % D2 % C5 % B4 % AB % BA % CD % b 1% E4 % D2 % EC % 22 & amp； fr=ala0

In fact, this chapter is relatively easy to understand, especially after you have learned the probability of high school. If you still don't understand it, you can ask me ... and I will try my best to help you. ...