check the picture below.
recall that in a square, all four sides are equal, therefore b = a.
so the perimeter is then 6√2 + 6√2 + 6√2 + 6√2, or 24√2.
Circumference = pi * diameter
diameter = 8.5; pi = 3.14
C = 3.14 * 8.5
C = 26.69 in = 26.7 in
So it our equation would be t(5)=5^2+2(5)
25+10=35 :)