Identify vertex and x intercepts of quadratic function:

$\displaystyle f(x) = x^2 - 8x + 16$

Book's answer:

$\displaystyle f(x) = (x - 4)^2$

x intercept $\displaystyle (4,0)$

vertex $\displaystyle (4,0)$

The answer I came up with using $\displaystyle f(x) = a(x - h)^2 + k$ :

$\displaystyle f(x) = 1(x^2 - 8x + 16) - (1)16 + 16$

$\displaystyle f(x) = x^2 -8x + 16$

I tried strait factoring as well to find the x intercept but got nowhere.

Any suggestions?