$\displaystyle x^2-8x+23-(x-p)^2+q$ for all values of x

find the value of p and q

I did

$\displaystyle (x^2-8x+16)+7=...\rightarrow (x+4)^2+7=(x+p)^2+q$

I'm stuck.. what should I do now, square route the whole thing?

edit:

whittled it down to

$\displaystyle 2x*2+23=p^2+q$

what now?