N = g/p, because you divide p by each side
A^2-64=0 you can factor like this:
(a+8)(a-8)=0 and since a>0, a must be 8
or you can do this:
add 64 to both sides of the equation leaving you with:
a^2=64 taking the square root of both sides
a=(-8,+8) and since a>0, a=8
