Respuesta :

edrush1957G
There must be added one zero pair: -9, 9.
f (x) = x² - 6 x + 9 - 9 + 1 = ( x² - 6 x + 9 ) - 8 =
=( x - 3 )² - 8 ( the vertex form)
ghanami
hello : 
x²-6x+1 =  x²-2(3)(x)+3²-3²+1 
             = (x-3)²-8...(.vertex form)