Respuesta :

for
ax^2+bx+c
if a=1 then
take 1/2 of b then square it, that will be c in the perfect square trionomial

1x^2-6x+c
a=1
b=-6
so
-6/2=-3, (-3)^2=9
c=9



x^2-6x+9
which factors to
(x-3)^2