اتحاد (a-b)(a+b)

we used Cartesian coordinate 2 dimensions and divide surface into four different positive and negative areas. areas number 1 and 3 are positive and area 2 and 4 are negative.
for identity a^2 minus b^2 will locate in areas number first and number fourth.
positive and negative ares
in order we will understand (a+b)(a-b) in visual and tangible for learning and understanding