input: Write a function that calculates the objective function of a linear equation ax + by = c. If the objective function is less than or equal to zero, return True; otherwise, return False.
  
  def linear_eq(a, b, c):
      return (a*x + b*y - c) <= 0
  
  assert linear_eq(3, 5, 7)==True
  assert linear_eq(3, 5, 4)==False
  assert linear_eq(2, 3, 1)==True
  assert linear_eq(1, 2, 2)==False
output: def linear_eq(a, b, c):
      return (a*x + b*y - c) <= 0