Y - Youth - using social networking allows you to connect on a deeper level with young people.
Y - Youth(年轻人)使用社交网络能让你与年轻人产生更深入的联系。
2
So, just to get you used to this idea, I'm going to draw a level surface of a function of three variables OK, so it's a surface given by the equation w of x, y, z equals some constant c.
为了令你们习惯于这个想法，我画一个三变量函数的等值面,这是一个平面,由函数w=c给出的。
3
Of course, start along the y-axis and then horizontally. That is the same level of difficulty.