>>14
1)
f(x) = (x-(a/2))^2 -(a/2)^2 +2
m = -(1/4)a^2 +2

2)
g(x) = -(x-((a-2)/2))^2 +(1/4)(a-2)^2 +a-3
= -(x-((a-2)/2))^2 +(1/4)a^2 -2
M = (1/4)a^2 -2

3)
m>M
-(1/4)a^2 +2 > (1/4)a^2 -2
a^2 < 16
-4 < a < 4