Question 851305
Your teacher meant that 1 might be a zero twice.
(x-1)^2 could be  a factor
f(x) = (x-1)^2 (x^2-4x+5)
(x-1)^2=0 x=1and  x=1
(x^2-4x+5)=0
x = 2+i
x = 2-i