def evaluate_polynomial_at(x, coefficients, prime)
      result = 0

      coefficients.each_with_index do |c, i|
        result += c * (x**i)
        result %= prime
      end

      result
    end
def evaluate_polynomial_at(x, coefficients, prime)
      result = 0

      coefficients.each_with_index do |c, i|
        result += c * (x**i)
        result %= prime
      end

      result
    end
FIXME : Needs focused tests
 Evaluate the polynomial at x.