Factor by grouping3ab-4b^2-4b+3a

Question

please help me understand this math problem

Answer 1

You have two sets of terms that look similar:
3ab and 3a
4b² and 4b

Let's group them together, then pull out a common factor:

(3ab + 3a) - (4b² + 4b) 

3a (b + 1) - 4b(b + 1)

We now have a common factor of (b + 1), so if we pull that out, we have

(b+1)(3a - 4b)