Quadratic Equations

quadratic_equation.rb

class QuadraticEquation
  attr_reader :x

  def initialize(a:, b:, c:)
    @a = a.to_f
    @b = b.to_f
    @c = c.to_f
    @x = result
  end

  def to_s
    a_str = @a != 1.0 ? "(#{@a})" : ''
    b_str = @b != 1.0 ? "(#{@b})" : ''
    c_str = "(#{@c})"
    x_str = x.join(', ')

    "formula: #{a_str}x^2 + #{b_str}x + #{c_str} = 0, x = (#{x_str})"
  end

  private

  def result
    x1, x2 = positive_x, negative_x

    if x1 == x2
      return [x1]
    else
      return [x1, x2]
    end
  end

  def positive_x
    (-@b + root(d)) / (2 * @a)
  end

  def negative_x
    (-@b - root(d)) / (2 * @a)
  end

  def d 
    (@b ** 2) - (4 * @a * @c)
  end

  def root(x)
    x.to_f ** (1.0 / 2.0) 
  end
end