The area of a rectangle (including squares) is defined as length times width or the equation:
A=l×w
However a square has the special property where length equals width which is represented by this equation:
l=w
So replace one of the variables with the other to get this new equation:
l×w=A
(w)×w=A
w^2=A
Often times for square the variable is represented as an s so:
s^2