(a - 7)*(a + 7) ---------------*(a + 7) a - 7
(((a - 7)*(a + 7))/(a - 7))*(a + 7) при a = -1
(((a - 7)*(a + 7))/(a - 7))*(a + 7)
((((-1) - 7)*((-1) + 7))/((-1) - 7))*((-1) + 7)
(((-1 - 7)*(-1 + 7))/(-1 - 7))*(-1 + 7)
36
2 (7 + a)
(7.0 + a)^2
2 49 + a + 14*a