The answer to that question is 3/7
Refer the attachment for your answer :)
6^2 = x (x - 9)
x^2 - 9x - 36 = 0
(x -12)(x + 3) = 0
x - 12 = 0; x = 12
x +3 = 0; x = -3
so in this case x = 12 then DC = 12 - 9 = 3
y^2 = 12^2 - 6^2
y^2 = 144 - 36
y^2 = 108
y = 10.4
The formula for the problem is: An = 8(n-1) - 2