Answer:
The maximum number of turns is 3
Step-by-step explanation:
The given function is
[tex]f(x)=x^4-x^3+3x+1[/tex]
The degree of this polynomial is 4.
If the degree of a given polynomial is n, then the polynomial has at least n-1 turns.
Therefore the number of turns of this 4th degree polynomial is at least 3.