What do you mean by "the sixth day, the ninth day" and "using two and using six" in the Book of Changes?

Six hexagrams, from bottom to top (taking Ganyao as an example), are the ninth day, the second day, the third day, the fourth day, the fifth day and the ninth day. Odd numbers are positive and even numbers are negative. So the sixth day shows that the first divination is Yin, and the ninth day shows that the first divination is Yang. The words "Yong" and "Jiong" in "Yong Jiu" mean "Tong". Because there are only six hexagrams and nine hexagrams in the two hexagrams of Gankun, which are pure yang and pure yin, but the extremes meet. Using nine and six tells us that poverty leads to change, change leads to communication, and the general rule lasts for a long time!