f(x)=-4x^2+4ax-4a-a^2
x=-4a/-8=a/2
1)a/2<0 a<0
f(x)max=f(1)=-4+4a-4a-a^2=-5
-4-a^2=-5
a=-1
2)0≤a/2≤10≤a≤2
f(x)max=f(a/2)=)=-a²+4a(a/2)-4a-a^2=-5
a=5/4
3)a/2>1a>2
f(x)max=f(0)=-4a-a^2=-5
a=1 a=-5
∴a=-1a=5/4