1. The problem statement, all variables and given/known data The problem states the following: Show that the points of space A(3,1,-5) B(8,3,3) and C(2,1,-4) are not colinear 2. Relevant equations I've tried to use the equation y2-y1=x2-x1 for the straight line on IR2 but since we are working in IR3 the same formula doesn't apply 3. The attempt at a solution I'm not sure how we calculate the slope of the straight line on IR3 or if there's another formula to demonstrate that the points are non colinear. Thanks in advance for the reply!