Answer:
B (2nd option)
Step-by-step explanation:
Factor each one.
6x^2+39x-21 is divisible by 3 -> 3(2x^2+13x-7) -> 3(2x-1)(x+7)
6x^2+54x+84 is divisble by 6 -> 6(x^2+9x+14) -> 6(x+2)(x+7)
The greatest common factor is 3(x+7), so taking that out of each polynomial, we have (2x-1) and 2(x+2). The least common multiple is the greatest common factor*(2x-1)*2(x+2) which, simplifying, is 12x^3+102x^2+114x-84, or B.
