If f(x)=x2−4x+3f(x) = x^2 - 4x + 3f(x)=x2−4x+3, solve f(f(x))<0f(f(x)) < 0f(f(x))<0.
1<x<31 < x < 31<x<3
2−2<x<2+22 - \sqrt{2} < x < 2 + \sqrt{2}2−2<x<2+2
x∈(2−2,1)∪(3,2+2)x \in (2-\sqrt{2}, 1) \cup (3, 2+\sqrt{2})x∈(2−2,1)∪(3,2+2)
No solution