If f(x)=x2−4x+3f(x) = x^2 - 4x + 3f(x)=x2−4x+3, solve f(x)≤−1f(x) \leq -1f(x)≤−1.
x = 2
x \in [1, 3]
x \in \emptyset
x \in (1, 3)