-4n*(n^2 -6n +3)
= (-4n)*n^2 +(-4n)*(-6n) +(-4n)*(3)
= -4n^3 +24n^2 -12n . . . . . . . . . . . . corresponds to selection B
Note that the signs alternate. For the first question the signs of the answer are the reverse of those of the original trinomial.
For the second question, multiplying by -n changes the signs back to those of the original trinomial. Only one answer has the signs correct, selection A.