input: from typing import Tuple
  
  def linear_eq_objective_function(coefficients: Tuple[float, float, float]) -> float:
      """ Calculate the objective function for a linear equation of the form ax + by = c.
      The input is a tuple of coefficients (a, b, c).
      
      >>> linear_eq_objective_function((3, 5, 7))
      -7
      >>> linear_eq_objective_function((1, 2, 3))
      -3
      """
      a, b, c = coefficients
      return a*x + b*y - c
output:     x, y = 0, 0
      return a * x + b * y - c