49/9
y=-x^2-4/3x+5
(h,k)
h = minimum
k/y = maximum
h = -b/2a
a = (-1)x^2
b = (-4/3)x
h = 4/3 / -2 = -2/3
To find the maximum, take the minimum and replace it with every "x" in the equation.
y = -(-2/3)^2-4/3(-2/3)+5
y = 49/9