Answer:

- (2a2b + 3ab + ab2)

Step-by-step explanation:

(-5a2b + 7ab2) - (a2b + 9ab2) = -6a2b - 2ab2

(4a2b - 3ab + ab2) + (-6a2b - 2ab2) = -2a2b - 3ab - ab2) = - (2a2b + 3ab + ab2)

a2 = a squared (a raise to 2)

b2 = b squared (b raise to 2)