They have also included videos so parents can refresh their knowledge of math when helping with homework.
他们还包括了视频，以便让家长在辅导孩子家庭作业时可以想起数学知识。
In 2006, Khan made homemade videos to help his ninth-grade cousin with math.
2006年，可汗自己制作视频，来帮助他九年级的表弟学习数学。
In 2006, Khan made homemade videos to help his ninth-grade cousin with math.
2006年，可汗自己制作视频，来帮助他九年级的表弟学习数学。
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