input: Write a function that calculates the objective function of a linear equation. Given coefficients a, b, and c, the function should return the result of the equation ax + by - c. If the input values are a = 3, b = 5, and c = 7, the function should return the value of ax + by - c.
  
  def linear_eq(a, b, c, x, y):
      return a*x + b*y - c
  
  assert linear_eq(3, 5, 7, 1, 1) == 1
  assert linear_eq(3, 5, 7, 2, 3) == 12 - 7
  assert linear_eq(3, 5, 7, 0, 0) == 0 - 7
  assert linear_eq(-2, 4, 10, 5, 3) == -10 + 12 - 10
output: def linear_eq(a, b, c, x, y):
      return a*x + b*y - c