Factor the trinomial below. x2 + 13x + 42 a. (x + 3)(x + 14) b. (x + 6)(x + 7) c. (x – 6)(x – 7) d. (x – 3)(x – 14)

To factor this we want to look at the multiples of 42
these are
42 and 1
21 and 2
14 and 3
6 and 7

we want to know which of these ads up to our middle coefficient which is 13.
we see that 6+7=13 so we can factor it into

because both operations are addition in the original form both will be addition in the factored form. For more information about how to choose + or - you can look into DeCartes law of signs.