Use the "ac method."

Multiply the leading coefficient by the constant term:

Now list all pairs of factors of -42:

1, -42

2, -21

3, -14

6, -7

7, -6

14, -3

21, -2

42, -1

Now which of these pairs sum to the coefficient of the linear term, in this case -19? The 2, -21 pair.

So rewrite -19 = 2 - 21 in your original expression:

-Dan