If the square of a-Ab = 9 and the square of ab-b = 4, then what is the square of A-B? What is the square of a + 2Ab + B

If the square of a-Ab = 9 and the square of ab-b = 4, then what is the square of A-B? What is the square of a + 2Ab + B

The first question is A2-B2 = a2-ab + ab-b2 = 9 + 4 = 13. The second question is wrong. It should be a2-2ab + B2, (a-b) 2 = a2-2ab + B2 = a2-ab - (ab-b2) = 9-4 = 5. If it is A2 + 2Ab + B2, let x (a2-ab) + y (ab-b2) = t (A2 + 2Ab + B2), expand the formula, x = - y = t, - x + y = 2T, x = y = 0 is not