Rectangular coordinate system, 

 Straight Lines - Slope of a line, Parallel and perpendicular lines, 

 Representations of a Line, General equations of a line, 

 Straight-line fit 

Rectangular Coordinate System

Equation of parallel and perpedicular lines in general form

Slope of a Line

Representation of a Line-1

 Representation of a Line-2

Parallel and Perpendicular Lines

General Equation of line

Straight Line Fit