Question 892254
The easy way for this one is factoring.


{{{y=-x^2+10x-16}}}
{{{y=-1(x^2-10x+16)}}}
{{{y=-1(x-2)(x-8)}}}


Zeros are at 2 and 8.
Line of symmetry is in the exact middle of those, at x=5.
The vertex is a maximum, at {{{y=-1(5-2)(5-8)=-1(3)(-3)=9}}} for the point (5,9).