OK, the correct answer is b2+4b−2+34b−6.
Note that when you subtract a multiple of 4b-6, you must change all of the terms. For 4b-6 to have a b^3, you should multiply 4b-6 by b^2 to get 4b^3 - 6b^2. You cannot directly change it to −4b3+4 like you did in the image.
Knowing this, you should be able to determine the answer.
- PM