Solutions of simultaneous equations
The HELM notes use Cramers rule. to solve systems of linear equations but that method is compu-
tationally very inefcient, with many repealed suhealeulatiol'ls. The tiECl'llliqUE presenter] here - Gauss
If the two lines form a right angle at their intersection they are said to be perpendicular.
For example, 3; : 2$+1 and y : %CC-l3 are perpendicular. Note the product of their slopes: (2) :
Key point: TWO straight lines y : at: + b and y : ca: + d