Very often students get asked to show whether 2 linear equations are parallel (or perpendicular – they meet at a 90° angle) to each other when drawn on a graph. In fact, the criteria for determining that 2 lines are parallel or perpendicular is quite simple.

2 lines are

PARALLELif thecoefficientsof thexvariableARE THE SAME.2 lines are

PERPENDICULARif thecoefficientsof thexvariableMULTIPLY TO -1

**Note**: The linear equations must be in the form **y =** **mx + c **that is the coefficient of the y-variable must be** 1** before attempting to determine if the lines are parallel or perpendicular.

Watch this short video for examples.