Write as a polynomial (a+2b) (4a-5b) - (3a-b) (b-a)

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