1. official website Purchase: official website, Li Dexin provided the purchase channel for this video. You can find the video purchase entrance on the homepage of the website and follow the prompts to buy.

2. Online video platform purchase: Video can also be purchased on online video platforms, such as Youku, iQiyi and Tencent Video.

3. Physical store purchase: Some physical bookstores or video stores may also sell them, so you can go to the store for consultation and purchase.

It should be noted that the source and copyright of the video should be confirmed before purchase to avoid being affected by copyright disputes. In addition, you can check the relevant comments and recommendations before buying, so as to better choose the video that suits you.

In a word, it is the safest way to buy Li Dexin's supporting videos through formal channels, which can avoid copyright problems and quality problems, and also support the creators' creation and development.