Given a + B = 1, A-B = - 3, find the value of a 2 + 3 AB + B 2

Given a + B = 1, A-B = - 3, find the value of a 2 + 3 AB + B 2

∵ a + B = 1, A-B = - 3, ∵ a = - 1, B = 2, then AB = - 2, ∵ A2 + 3AB + B2 = (a + b) 2 + AB = 1-2 = - 1