Answer:
7a^2-ab-9b^2
Step-by-step explanation:
Let's do this in two steps. First, we multiply the first two parentheses:
(a+2b)(4a-5b)
4a^2-5ab+8ab-10b^2 = 4a^2+3ab-10b^2
Then, do the other two parentheses:
(3a-b)(b-a)
3ab-3a^2-b^2+ab = 4ab-3a^2-b^2
Then, combine them:
4a^2+3ab-10b^2-4ab+3a^2+b^2 = 7a^2-ab-9b^2
