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
[tex](x + 7)(x + 6)[/tex]
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.
