Explicación paso a paso:
Solo debemos reemplazar así:
A @ B = (A + B)² - 4
(2 @ 1) = (2 + 1)² - 4 = ( 3²- 4) = 9 - 4 = 5
(2 @ 1) @ 1 = 5 @ 1 = (5 + 1)² - 4 = 6²-4 = 36 - 4 = 32
