Fill the blank with a constant, so that the resulting expression can be factored as the product of two linear expressions:
3ab - 12a + 7b + __
This isn't the same question, but this will definitely help.
This is a good answer Cal. Thanks
3ab - 12a + 7b + ____
3a ( b - 4) + 7 ( b - 4) =
(3a + 7) ( b - 4)
3ab -12a + 7b + - 28