The Y-coordinate of a point is its location along the Y-axis. If the point is above the x-axis, its y-coordinate is positive, and if the point is below the x-axis, Its y-coordinate is negative,so the point labeled 2,2 is 2 the right and 2 above the origin. Every point on a plane has two coordinates. because its the center of the plane the origin gets the coordinates 0,0. The coordinates of all other points indicate how far they are from the origin.
Distance formula: d= x2-x1)2 + Y2-Y1)2
slope formula: Y2-Y1/X2-X1
midpoint formula: x,y= x1+x2, y1+y2
Coordinate Geometry: An Introduction
Core 1 - Coordinate Geometry (1) - Introduction to straight line equations