(a - 2)*(a + 2) + 4
(a - 2)*(a + 2) + 4 при a = 2
((2) - 2)*((2) + 2) + 4
(2 - 2)*(2 + 2) + 4
4
4.0 + (2.0 + a)*(-2.0 + a)
2 a