Answer:
(4b + 5)
Explanation:
To get 4b^2 you already have b^2 if you put b inside the second set of brackets. But that would mean you don't have 4 anywhere to get 4b^2.
So the first step has to be
(b + 3)(4b
Now look at the 15 for a moment. It is plus 15. The only way you can get a plus 15 is if both signs are plus (after the b terms) or both terms are minus.
The middle term (17b) is plus so both terms after b are plus.
(b + 3)(4b +
Now we need something that multiplies to 15. 3*5 = 15. So the term you want is 5.
(b + 3)(4b + 5)
Does the middle term work?
5*b + 3*4b = 5b + 12b = 17b
Everything looks fine.
The second factor is 17b.