By looking at linear equations we can tell how they will interact in the coordinate plane. Which of the following are possible if two linear equations are graphed? They could be parallel to each other. They could intersect at two points. They could be perpendicular to each other. They could be skew lines. They could be the same line.
In a coordinate plane (2 dimensions), two lines are parallel or perpendicular or the same line. In three dimensions, the lines are parallel or perpendicular or skew. Two straight lines never intersect at more than one point.
