Hello from MrBillDoesMath!
Answer:
The topmost (blue shaded) rectangle.
Discussion:
Order the terms in each parentheses by decreasing exponent order:
(
6b^3 + 6 - b^4) - (8b^3-6b^4+ 2) =
( - b^4 + 6b^3 + 6) - ( -6b^4 + 8b^3 + 2) =>
Look at the second parentheses. Recall that the product of two negative values is positive so the above expression equals
( - b^4 + 6b^3 + 6) + ( 6b^4 - 8b^3 - 2)
Combine like terms from both parentheses:
(-b^4+ 6b^4) + (6b^3-8b^3) + (6 - 2) => simplify
5b^4 + ( -2b^3) + 4 =>
5b^4 -2b^3 + 4
This is the topmost (blue shaded) rectangle.
Thank you,
MrB
