input: Write a function to find the x-intercepts of a quadratic equation.
  assert quadratic_x_intercept(1, 4, -5) == (1.0, -5.0)
  assert quadratic_x_intercept(1, -3, 2) == (2.0, 1.0)
  assert quadratic_x_intercept(1, 2, 5) == 'No real solutions exist!'
output: def quadratic_x_intercept(a, b, c):
      import math
      discriminant = b**2 - 4*a*c
      if discriminant < 0:
          return 'No real solutions exist!'
      x1 = (-b + math.sqrt(discriminant)) / (2*a)
      x2 = (-b - math.sqrt(discriminant)) / (2*a)
      return (x1, x2)