In this problem, I get 2a - a - 5 on the top, while greg changes it to 2a - a + 5. Does the negative need to be distributed? There are no parentheses around the top. Confused.
first_term - second_term can be rewritten as:
first_term + (-1) * ( second_term)
the first term here is 2a, and the second term is a - 5. If you look closely then, we’re trying to find the negative of the entire second term.
The “negative” of a - 5 is 5 - a, and so you have:
2a + 5 - a
The parentheses are implicit because we wanted the negative of an entire term by default.