ANSWER
a.
positive
EXPLANATION
The given binomial expansion is:
[tex] {(x - y)}^{n} [/tex]
We can see that the second term is negative (-y).
When we expand this binomial for n=3,4, and 5, the sign is got to alternate.
The first term is positive
The second term negative
The third term is positive
The first choice is correct.
