Hello from MrBillDoesMath!
Answer:
x = 5 only
Discussion:
x^2 - 10x + 25.
Note that (-5)*(-5) = 25, the constant term in f(x), and -5 + -5 = -10, the coefficient of x in f(x). This suggests that the factorization of f(x) is
f(x) = (x-5)^2
Hence f has a single (repeated or double) root, x = 5, which is Choice D
Thank you,
MrB
