Given a + B = 5, ab = 1.5, find the square of a + B (a-b)

Given a + B = 5, ab = 1.5, find the square of a + B (a-b)

Application of complete square formula
A + B = (a + b) - 2Ab = 25-3 = 22
(a-b) square = (a + b) square-4ab = 19