Giải phương trình vi phân a) x(1+ y2 2) dx + y(1+ x2 2) dy = 0;
1 ln x
b) y− x y = x với điều kiện ban đầu y x=1 = 0

Nour and rana are shopping for a christmas tree. they are deciding between 2 22 different types of trees (real and fake) and 4 44 colors for the ornaments (white, silver, gold, and purple). they each created a display to represent the sample space of randomly picking a type of tree and a color for the ornaments. whose display correctly represents the sample space?