Way too much work.

  def fib_binet(n)
    a = (1+Math.sqrt(5))**n
    b = (1-Math.sqrt(5))**n
    c = (2**n)*Math.sqrt(5)
    return ((a-b)/c).truncate()
  end

  def fib2(n)
    a = Math.sqrt(5)
    return ((1/a)*(((1+a)/2)**n)).round()
  end
  (0..20).each do | i |
    puts fib_binet(i)
    puts fib2(i)
  end