help i am confused and im not sure how to answer this

Answer:
y=(x-4)²
Step-by-step explanation:
(a-b)²=a²-2ab+b²
(x-4)²=x²-2×x×4+4²
(x-4)²=x²-8x+16
Answer:
y=(x-4)²+1.
Step-by-step explanation:
1) if to re-write the given equation y=x²-8x+C, then 'No Roots' is possible, if C>16;
2) among the given answers the only has 'No roots', it is y=(x-4)²+1, in it C=17.