Final answer:
The incorrect mathematical representation of the relation 'the second number is 1 less than three times the first number' is y = 1 - 3x, as it suggests a different relationship than the one described.
Step-by-step explanation:
The question is asking to find which expression does not correctly represent the relation "the second number is 1 less than three times the first number". The correct mathematical representation for this relation is y = 3x - 1. We can evaluate the given equations one by one: The first option y = 3x + (-1) simplifies to y = 3x - 1, which is the correct representation. The second option y = -1 + 3x also simplifies to y = 3x - 1, again representing the relation accurately. The third option is y = 3x - 1, which is explicitly the correct form of the relation.
The fourth option, however, is y = 1 - 3x, which does not represent the relation correctly as it would mean that the second number is 1 minus three times the first number, which is not equivalent to being 1 less than three times the first number. Therefore, the incorrect representation of the given relation is y = 1 - 3x.