4: The function has a maximum of how many turns in its graph?

Given:
[tex]f(x)=-x^4+4x^2-2[/tex]To determine the maximum turns of the given function in its graph, we first note that the maximum number of turning points of a polynomial function is always one less than the degree of the function. Based on the given function, the degree is 4, so the turning points must be:
[tex]Turning\text{ points = 4-1=3}[/tex]We can double check this by graphing the function as shown below:
As we can see, there are 3 turns in its graph. Therefore, the answer is: D. 3