Method 1: Take two points to establish a straight line, and calculate the analytical expression of the straight line. Substitute the coordinates of the third point to see if it satisfies the analytical expression (straight line and equation).

Method 2: Let the three points be A, B, and C. Use vectors to prove that: λAB=AC (where λ is a non-zero real number).

Method 3: Use the point difference method to find the slope of AB and the slope of AC. If they are equal, the three points are collinear.

Method 4: Use Menelaos' theorem.

Method 5: Use the axiom in geometry: "If two non-coincident planes have a common point, then they have one and only one common straight line passing through that point." It can be seen that if three points belong to two intersecting planes, then the three points are collinear.

Method 6: Use the theorem "through a point outside a straight line there is only one straight line parallel (perpendicular) to the known straight line". It is actually the same method.

Method 7: Prove that the angle is 180°.

Method 8: Let ABC, prove that the area of ​​△ABC is 0.