f^2-4f=8
Solve: f2 - 4f = 8
f2 - 4f - 8 = 0
Using the quadratic formula: a = 1 b = -4 c = -8
f = [ 4 + sqrt(16 +32) ] / 2 ---> [ 4 + 4sqrt(3) ] / 2 = 2 + 2sqrt(3)
f = [ 4 - sqrt(16 +32) ] / 2 ---> [ 4 - 4sqrt(3) ] / 2 = 2 - 2sqrt(3)