To find the x coordinate of the vertex,
x = [tex] \frac{-b}{2a} [/tex]
In this case, a = 4 and b = -6. Sub these values into the equation,
x = [tex] \frac{-(-6)}{2(4)} [/tex]
= 2
Sub x = 2 back into the original equation,
[tex]4(2)^{2} -16(2)+5[/tex]
= -11
Therefore, your vertex is V(2, -11)
Hope this helped!